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Research ArticleGeneral Decay and Blow-Up of Solutions for a System ofViscoelastic Equations of Kirchhoff Type with Strong Damping
Wenjun Liu Gang Li and Linghui Hong
College of Mathematics and Statistics Nanjing University of Information Science and Technology Nanjing 210044 China
Correspondence should be addressed to Wenjun Liu wjliunuisteducn
Received 8 May 2013 Revised 28 September 2013 Accepted 16 November 2013 Published 4 February 2014
Academic Editor William Ziemer
Copyright copy 2014 Wenjun Liu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
The general decay and blow-up of solutions for a system of viscoelastic equations of Kirchhoff type with strong damping isconsidered We first establish two blow-up results one is for certain solutions with nonpositive initial energy as well as positiveinitial energy by exploiting the convexity technique the other is for certain solutions with arbitrarily positive initial energy basedon the method of Li and Tsai Then we give a decay result of global solutions by the perturbed energy method under a weakerassumption on the relaxation functions
1 Introduction
In this work we investigate the following system of viscoelas-tic equations of Kirchhoff type
119906119905119905minus119872(nabla119906
2
2) Δ119906 + int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) d119904 minus Δ119906
119905
= 1198911(119906 V) (119909 119905) isin Ω times (0infin)
V119905119905minus119872(nablaV2
2) ΔV + int
119905
0
1198922(119905 minus 119904) ΔV (119904) d119904 minus ΔV
119905
= 1198912(119906 V) (119909 119905) isin Ω times (0infin)
119906 (119909 119905) = 0 V (119909 119905) = 0
(119909 119905) isin 120597Ω times [0infin)
119906 (119909 0) = 1199060(119909) 119906
119905(119909 0) = 119906
1(119909) 119909 isin Ω
V (119909 0) = V0(119909) V
119905(119909 0) = V
1(119909) 119909 isin Ω
(1)
where Ω sub R119899 119899 ge 1 is a bounded domain with smoothboundary 120597Ω119872 is a positive locally Lipschitz functionand 119892
119894(sdot) R+ rarr R+ (119894 = 1 2) (119891
1 1198912) R2 rarr R2 are
given functions to be specified later
To motivate our work let us recall some previous resultsregarding viscoelastic equations of Kirchhoff type The fol-lowing problem
119906119905119905minus119872(nabla119906
2
2) Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 + ℎ (119906119905) = 119891 (119906)
(119909 119905) isin Ω times (0infin)
119906 = 0 (119909 119905) isin 120597Ω times [0infin)
119906 (119909 0) = 1199060(119909) 119906
119905(119909 0) = 119906
1(119909) 119909 isin Ω
(2)
is a model to describe the motion of deformable solidsas hereditary effect is incorporated It was first studiedby Torrejon and Yong [1] who proved the existence of aweakly asymptotic stable solution for large analytical datumLater Munoz Rivera [2] showed the existence of globalsolutions for small datum and the total energy decays to zeroexponentially under some restrictions Then Wu and Tsai[3] treated problem (2) for ℎ(119906
119905) = minusΔ119906
119905and proved the
global existence decay and blow-up with suitable conditionson initial data They obtained the blow-up properties oflocal solution with small positive initial energy by the directmethod of [4] To obtain the decay result they assumed thatthe nonnegative kernel 1198921015840(119905) le minus119903119892(119905) forall119905 ge 0 for some 119903 gt
0 This energy decay result was recently improved by Wu
Hindawi Publishing CorporationJournal of Function SpacesVolume 2014 Article ID 284809 21 pageshttpdxdoiorg1011552014284809
2 Journal of Function Spaces
in [5] under a weaker condition on 119892 (ie 1198921015840(119905) le 0 for119905 ge 0) For a single wave equation of Kirchhoff type withoutthe viscoelastic term we refer the reader to Matsuyama andIkehata [6] and Ono [7ndash10]
Many results concerning local existence global existencedecay and blow-up of solutions for a system of waveequations of Kirchhoff type without viscoelastic terms (ie119892119894
= 0 119894 = 1 2) have also been extensively studiedFor example Park and Bae [11] considered the system ofwave equations with nonlinear dampings for 119891
1(119906 V) =
120583|119906|119902minus1
119906 and 1198912(119906 V) = 120583|V|119902minus1V 119902 ge 1 and showed the
global existence and asymptotic behavior of solutions undersome restrictions on the initial energy Later Benaissa andMessaoudi [12] discussed blow-up properties for negativeinitial energy Recently Wu and Tsai [13] studied the system(1) for 119892
119894= 0 (119894 = 1 2) Under some suitable assumptions
on 119891119894(119894 = 1 2) they proved local existence of solutions by
applying the Banach fixed point theorem and the blow-up ofsolutions by using the method of Li and Tsai in [4] wherethree different cases on the sign of the initial energy 119864(0) areconsidered
In the case of 119872 equiv 1 and in the presence of viscoelasticterm (ie 119892 = 0) Cavalcanti et al [14] studied the equationthat was subject to a locally distributed dissipation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 + 119886 (119909) 119906119905+ |119906|120574119906 = 0
(119909 119905) isin Ω times (0infin)
(3)
with the same initial and boundary conditions as that of (2)and proved an exponential decay rate This work extendedthe result of Zuazua [15] in which he considered (3) with119892 = 0 and the localized linear damping By using thepiecewise multipliers method Cavalcanti and Oquendo [16]investigated the equation
119906119905119905minus 1198960Δ119906 + int
119905
0
div [119886 (119909) 119892 (119905 minus 119904) nabla119906 (119904)] d119904
+ 119887 (119909) ℎ (119906119905) + 119891 (119906) = 0 (119909 119905) isin Ω times (0infin)
(4)
with the same initial and boundary conditions as that of (2)Under the similar conditions on the relaxation function 119892 asabove and 119886(119909) + 119887(119909) ge 120575 gt 0 for all 119909 isin Ω they improvedthe results of [14] by establishing exponential stability forexponential decay function 119892 and linear function ℎ andpolynomial stability for polynomial decay function 119892 andnonlinear function ℎ respectively
Concerning blow-up results Messaoudi [17] consideredthe equation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 + 119886119906119905
1003816100381610038161003816119906119905
1003816100381610038161003816
119898minus2
= 119887|119906|119903minus2
119906
(119909 119905) isin Ω times (0infin)
(5)
He proved that any weak solution with negative initial energyblows up in finite time if 119903 gt 119898 and
int
infin
0
119892 (119904) d119904 le 119903 minus 2
119903 minus 2 + 1119903
(6)
while exists globally for any initial data in the appropriatespace if 119898 ge 119903 This result was improved by the same authorin [18] for positive initial energy under suitable conditions on119892 119898 and 119903 Recently Liu [19] studied the equation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 minus 120596Δ119906119905+ 120583119906119905= |119906|119903minus2
119906
(119909 119905) isin Ω times (0infin)
(7)
with the same initial and boundary condition as that of (2)By virtue of convexity technique and supposing that
int
infin
0
119892 (119904) d119904 le 119903 minus 2
119903 minus 2 + 1 [(1 minus120575)
2
119903 + 2120575 (1 minus120575)]
(8)
where 120575 = max0 120575 he proved that the solution with
nonpositive initial energy as well as positive initial energyblows up in finite time
We should mention that the following system
119906119905119905minus Δ119906 + int
119905
0
1198921(119905 minus 120591) Δ119906 (120591) d120591 + 1003816
100381610038161003816119906119905
1003816100381610038161003816
119898minus1
119906119905= 1198911(119906 V)
(119909 119905) isin Ω times (0 119879)
V119905119905minus ΔV + int
119905
0
1198922(119905 minus 120591) ΔV (120591) d120591 + 1003816
100381610038161003816V119905
1003816100381610038161003816
120574minus1V119905= 1198912(119906 V)
(119909 119905) isin Ω times (0 119879)
119906 (119909 119905) = 0 V (119909 119905) = 0
(119909 119905) isin 120597Ω times [0 119879)
119906 (119909 0) = 1199060(119909) 119906
119905(119909 0) = 119906
1(119909) 119909 isin Ω
V (119909 0) = V0(119909) V
119905(119909 0) = V
1(119909) 119909 isin Ω
(9)
was considered by Han and Wang in [20] where Ω is abounded domain with smooth boundary 120597Ω in R119899 119899 =
1 2 3Under suitable assumptions on the functions119892119894 119891119894(119894 =
1 2) the initial data and the parameters in the above problemestablished local existence global existence and blow-upproperty (the initial energy 119864(0) lt 0) This latter blow-upresult has been improved byMessaoudi and Said-Houari [21]into certain solutions with positive initial energy RecentlyLiang and Gao in [22] investigated the following problem
119906119905119905minus Δ119906 + int
119905
0
1198921(119905 minus 120591)Δ119906 (120591) d120591 minus Δ119906
119905= 1198911(119906 V)
(119909 119905) isin Ω times (0 119879)
V119905119905minus ΔV + int
119905
0
1198922(119905 minus 120591)ΔV (120591) d120591 minus ΔV
119905= 1198912(119906 V)
(119909 119905) isin Ω times (0 119879)
(10)
with the same initial and boundary conditions as that of (9)Under suitable assumptions on the functions 119892
119894 119891119894(119894 = 1 2)
Journal of Function Spaces 3
and certain initial data in the stable set they proved that thedecay rate of the solution energy is exponential Converselyfor certain initial data in the unstable set they proved thatthere are solutions with positive initial energy that blow upin finite time It is also worth mentioning the work [23] inwhich we studied system (1) Under suitable assumptions onthe functions 119892
119894 119891119894(119894 = 1 2) and certain initial conditions
we showed that the solutions are global in time and the energydecays exponentially For other papers related to existenceuniform decay and blow-up of solutions of nonlinear waveequations we refer the reader to [14 24ndash29] for existence anduniform decay to [17 30ndash34] for blow-up and to [35ndash40] forthe coupled system To the best of our knowledge the generaldecay and blow-up of solutions for systems of viscoelasticequations of Kirchhoff type with strong damping have notbeen well studied
Motivated by the above mentioned research we con-sider in the present work the coupled system (1) withnonzero 119892
119894(119894 = 1 2) and nonconstant 119872(119904) We note that
in such a coupled system case we should overcome the addi-tional difficulties brought by the treatment of the nonlinearcoupled terms We first establish two blow-up results one isfor certain solutions with nonpositive initial energy as wellas positive initial energy the other is for certain solutionswith arbitrarily positive initial energy Then we give a decayresult of global solutions under a weaker assumption on therelaxation functions 119892
119894(119905) (119894 = 1 2)
This paper is organized as follows In the next section wepresent some assumptions notations and known results andstate the main results Theorems 4 5 6 and 7 The two blow-up results Theorems 5 and 6 are proved in Sections 3 and4 respectively Section 5 is devoted to the proof of the decayresultmdashTheorem 7
2 Preliminaries and Main Result
In this section we present some assumptions notations andknown results and state the main results First we make thefollowing assumptions(A1) 119872(119904) is a positive locally Lipschitz function for 119904 ge
0 with the Lipschitz constant 119871 satisfying
119872(119904) ge 1198980gt 0 (11)
(A2) 119892119894(119905) [0infin) rarr (0infin) (119894 = 1 2) are strictly
decreasing 1198621 functions such that
1198980minus int
infin
0
119892119894(119904) d119904 = 119897
119894gt 0 (12)
(A3) There exist two positive differentiable functions 1205851(119905)
and 1205852(119905) such that
1198921015840
119894(119905) le minus120585
119894(119905) 119892119894(119905) (119894 = 1 2) for 119905 ge 0 (13)
and 120585119894(119905) satisfies
1205851015840
119894(119905) le 0 forall119905 gt 0 int
+infin
0
120585119894(119905) d119905 = infin (119894 = 1 2)
(14)
(A4) We make the following extra assumption on 119872
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904 ge 2 (119901 + 1)1198980119904 forall119904 ge 0 (15)
where 119872(119904) = int
119904
0119872(120591)d120591
Remark 1 It is clear that 119872(119904) = 1198980+ 1198981119904120574 (which occurs
physically in the study of vibrations of damped flexible spacestructures in a bounded domain in R119899) satisfies (A4) for 119904 ge0 1198980gt 0 119898
1ge 0 120574 ge 0 as long as 119901 + 1 gt 120574 Indeed by
straightforward calculations we obtain
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904
= 2 (119901 + 2) (1198980119904 +
1198981
120574 + 1
119904120574+1
) minus 21198980119904 minus 2119898
1119904120574+1
= 2 (119901 + 1)1198980119904 +
2 (119901 + 1 minus 120574)
120574 + 1
1198981119904120574+1
ge 2 (119901 + 1)1198980119904
(16)
Next we introduce some notations Consider
(119892119894 nabla119908) (119905) = int
119905
0
119892119894(119905 minus 119904) nabla119908 (119905) minus nabla119908 (119904)
2
2d119904
119897 = min 1198971 1198972
1198920(119905) = max 119892
1(119905) 1198922(119905) forall119905 ge 0
sdot119902= sdot119871119902(Ω)
1 le 119902 le infin
(17)
the Hilbert space 1198712(Ω) endowed with the inner product
(119906 V) = int
Ω
119906 (119909) V (119909) d119909 (18)
and the functions 1198911(119906 V) and 119891
2(119906 V) (see also [21])
1198911(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901119906|V|119901+2]
1198912(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901+2|V|119901V]
(19)
where 119886 119887 gt 0 are constants and 119901 satisfies
minus 1 lt 119901 if 119899 = 1 2
minus 1 lt 119901 le
(3 minus 119899)
(119899 minus 2)
if 119899 ge 3
(20)
One can easily verify that
1199061198911(119906 V) + V119891
2(119906 V) = 2 (119901 + 2) 119865 (119906 V) forall (119906 V) isin R
2
(21)
where
119865 (119906 V) =1
2 (119901 + 2)
[119886|119906 + V|2(119901+2) + 2119887|119906V|119901+2] (22)
Then we give two lemmas which will be used throughoutthis work
4 Journal of Function Spaces
Lemma 2 (Sobolev-Poincare inequality [41]) If 2 le 120588 le
2119899(119899 minus 2) then
119906120588le 119862nabla119906
2for 119906 isin 119867
1
0(Ω) (23)
holds with some constant 119862
Lemma 3 ([21 Lemma 32]) Assume that (20) holds Thenthere exists 120578
1gt 0 such that for any (119906 V) isin (119867
1
0(Ω) cap
1198672(Ω)) times (119867
1
0(Ω) cap 119867
2(Ω)) one has
119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
le 1205781(1198971nabla1199062
2+ 1198972nablaV22)
119901+2
(24)
We now state a local existence theorem for system (1)whose proof follows the arguments in [3 13]
Theorem 4 Suppose that (20) (1198601) and (1198602) hold andthat 119906
0 V0
isin 1198671
0(Ω) cap 119867
2(Ω) and 119906
1 V1
isin 1198712(Ω) Then
problem (1) has a unique local solution
119906 V isin 119862 ([0 119879) 1198671
0(Ω) cap 119867
2(Ω))
119906119905 V119905isin 119862 ([0 119879) 119871
2(Ω)) cap 119871
2([0 119879) 119867
1
0(Ω))
(25)
for some 119879 gt 0 Moreover at least one of the followingstatements is valid
(1) 119879 = infin
(2) lim119905rarr119879
minus
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ Δ119906
2
2+ ΔV2
2) = infin
(26)
The energy associated with system (1) is given by
119864 (119905) =
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1
2
(int
119905
0
1198921(119904) d119904) nabla119906
2
2
minus
1
2
(int
119905
0
1198922(119904) d119904) nablaV2
2minus int
Ω
119865 (119906 V) d119909
+
1
2
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2
119872(nabla1199062
2) +
1
2
119872(nablaV22) for 119905 ge 0
(27)
As in [5] we can get
1198641015840(119905)
= minus (1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2) minus
1
2
[1198921(119905) nabla119906
2
2+ 1198922(119905) nablaV2
2]
+
1
2
[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)] le 0 forall119905 ge 0
(28)
Then we have
119864 (119905) = 119864 (0) minus int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
minus
1
2
int
119905
0
[1198921(120591) nabla119906 (120591)
2
2+ 1198922(120591) nablaV (120591)2
2] d120591
+
1
2
int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
(29)
We introduce
1198611= 12057812(119901+2)
1 120572
lowast= 119861minus(119901+2)(119901+1)
1
1198641= (
1
2
minus
1
2 (119901 + 2)
)1205722
lowast
(30)
where 1205781is the optimal constant in (24)
Our first result is concerned with the blow-up for certainlocal solutions with nonpositive initial energy as well aspositive initial energy
Theorem 5 Assume that (1198601)-(1198602) (1198604) and (20) hold Let(119906 V) be the unique local solution to system (1) For any fixed120575 lt 1 assuming that we can choose (119906
0 V0) (1199061 V1) satisfy
119864 (0) lt 1205751198641 (119897
1
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (31)
Suppose further that
int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus120575)
2
(119901 + 2) +120575 (1 minus
120575)]
(119894 = 1 2)
(32)
where 120575 = max0 120575 then 119879 lt infin
Our second result shows that certain local solutions witharbitrarily positive initial energy can also blow up
Theorem 6 Suppose that (A1)-(A2) (A4) (20) and
int
infin
0
119892119894(119904) d119904 le
2 (119901 + 1)1198980
2 (119901 + 1) + 12 (119901 + 2)
(119894 = 1 2) (33)
Journal of Function Spaces 5
hold Assume further that 1199060 V0isin 1198671
0(Ω)cap119867
2(Ω) and 119906
1 V1isin
1198712(Ω) and satisfy
0 lt 119864 (0)
lt min
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(34)
then the solution of problem (1) blows up at a finite time 119879lowast inthe sense of (119) belowMoreover the upper bounds for119879lowast canbe estimated by
119879lowastle 2(3119901+5)2(119901+1)
(119901 + 1) 119888
2radic1198861
1 minus [1 + 119888ℎ (0)]minus1(119901+1)
(35)
where ℎ(0) = [11990602
2+ V02
2+ 1198791(nabla11990602
2+ nablaV
02
2)]minus(119901+1)2
and 1198861is given in (116) below
Finally we state the general decay result For conveniencewe choose especially 119872(119904) = 119898
0+ 1198981119904120574 1198980gt 0 119898
1ge 0
and 120574 ge 0 Then the energy functional 119864(119905) defined by (27)becomes
119864 (119905) = 119864 (119906 (119905) V (119905))
=
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(36)
Theorem 7 Suppose that (20) (1198601)-(1198602) and (1198603) holdand that (119906
0 1199061) isin (119867
1
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and (V
0 V1) isin
(1198671
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and satisfy 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (37)
Then for each 1199050gt 0 there exist two positive constants 119870 and
119896 such that the energy of (1) satisfies
119864 (119905) le 119870119890minus119896int119905
1199050120585(119904)d119904
119905 ge 1199050 (38)
where 120585(119905) = min1205851(119905) 1205852(119905)
To achieve general decay result we will use a Lyapunovtype technique for some perturbation energy following themethod introduced in [42] This result improves the one inLi et al [23] in which only the exponential decay rates areconsidered
3 Blow-Up of Solutions with InitialData in the Unstable Set
In this section we prove a finite time blow-up result for initialdata in the unstable set We need the following lemmas
Lemma 8 Suppose that (20) (1198601) (1198602) and (1198604) hold Let(119906 V) be the solution of system (1) Assume further that 119864(0) lt1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (39)
Then there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 for 119905 isin [0 119879) (40)
Proof We first note that by (27) (24) and the definition of1198611 we have
119864 (119905) ge
1
2
(1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+
1
2
(1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1198612(119901+2)
1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
=
1
2
1205722minus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
= 119866 (120572)
(41)
where we have used 119872(119904) = int
119904
0119872(120591)d120591 ge 119898
0119904 ge 0 and
120572 = (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
(42)
It is easy to verify that119866(120572) is increasing in (0 120572lowast) decreasing
in (120572lowastinfin) and that 119866(120572) rarr minusinfin as 120572 rarr infin and
119866(120572)max = 119866 (120572lowast) =
1
2
1205722
lowastminus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
lowast= 1198641 (43)
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Mathematical Problems in Engineering
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Differential EquationsInternational Journal of
Volume 2014
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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OptimizationJournal of
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CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
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Operations ResearchAdvances in
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Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
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Algebra
Discrete Dynamics in Nature and Society
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Discrete MathematicsJournal of
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
2 Journal of Function Spaces
in [5] under a weaker condition on 119892 (ie 1198921015840(119905) le 0 for119905 ge 0) For a single wave equation of Kirchhoff type withoutthe viscoelastic term we refer the reader to Matsuyama andIkehata [6] and Ono [7ndash10]
Many results concerning local existence global existencedecay and blow-up of solutions for a system of waveequations of Kirchhoff type without viscoelastic terms (ie119892119894
= 0 119894 = 1 2) have also been extensively studiedFor example Park and Bae [11] considered the system ofwave equations with nonlinear dampings for 119891
1(119906 V) =
120583|119906|119902minus1
119906 and 1198912(119906 V) = 120583|V|119902minus1V 119902 ge 1 and showed the
global existence and asymptotic behavior of solutions undersome restrictions on the initial energy Later Benaissa andMessaoudi [12] discussed blow-up properties for negativeinitial energy Recently Wu and Tsai [13] studied the system(1) for 119892
119894= 0 (119894 = 1 2) Under some suitable assumptions
on 119891119894(119894 = 1 2) they proved local existence of solutions by
applying the Banach fixed point theorem and the blow-up ofsolutions by using the method of Li and Tsai in [4] wherethree different cases on the sign of the initial energy 119864(0) areconsidered
In the case of 119872 equiv 1 and in the presence of viscoelasticterm (ie 119892 = 0) Cavalcanti et al [14] studied the equationthat was subject to a locally distributed dissipation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 + 119886 (119909) 119906119905+ |119906|120574119906 = 0
(119909 119905) isin Ω times (0infin)
(3)
with the same initial and boundary conditions as that of (2)and proved an exponential decay rate This work extendedthe result of Zuazua [15] in which he considered (3) with119892 = 0 and the localized linear damping By using thepiecewise multipliers method Cavalcanti and Oquendo [16]investigated the equation
119906119905119905minus 1198960Δ119906 + int
119905
0
div [119886 (119909) 119892 (119905 minus 119904) nabla119906 (119904)] d119904
+ 119887 (119909) ℎ (119906119905) + 119891 (119906) = 0 (119909 119905) isin Ω times (0infin)
(4)
with the same initial and boundary conditions as that of (2)Under the similar conditions on the relaxation function 119892 asabove and 119886(119909) + 119887(119909) ge 120575 gt 0 for all 119909 isin Ω they improvedthe results of [14] by establishing exponential stability forexponential decay function 119892 and linear function ℎ andpolynomial stability for polynomial decay function 119892 andnonlinear function ℎ respectively
Concerning blow-up results Messaoudi [17] consideredthe equation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 + 119886119906119905
1003816100381610038161003816119906119905
1003816100381610038161003816
119898minus2
= 119887|119906|119903minus2
119906
(119909 119905) isin Ω times (0infin)
(5)
He proved that any weak solution with negative initial energyblows up in finite time if 119903 gt 119898 and
int
infin
0
119892 (119904) d119904 le 119903 minus 2
119903 minus 2 + 1119903
(6)
while exists globally for any initial data in the appropriatespace if 119898 ge 119903 This result was improved by the same authorin [18] for positive initial energy under suitable conditions on119892 119898 and 119903 Recently Liu [19] studied the equation
119906119905119905minus Δ119906 + int
119905
0
119892 (119905 minus 119904) Δ119906 (119904) d119904 minus 120596Δ119906119905+ 120583119906119905= |119906|119903minus2
119906
(119909 119905) isin Ω times (0infin)
(7)
with the same initial and boundary condition as that of (2)By virtue of convexity technique and supposing that
int
infin
0
119892 (119904) d119904 le 119903 minus 2
119903 minus 2 + 1 [(1 minus120575)
2
119903 + 2120575 (1 minus120575)]
(8)
where 120575 = max0 120575 he proved that the solution with
nonpositive initial energy as well as positive initial energyblows up in finite time
We should mention that the following system
119906119905119905minus Δ119906 + int
119905
0
1198921(119905 minus 120591) Δ119906 (120591) d120591 + 1003816
100381610038161003816119906119905
1003816100381610038161003816
119898minus1
119906119905= 1198911(119906 V)
(119909 119905) isin Ω times (0 119879)
V119905119905minus ΔV + int
119905
0
1198922(119905 minus 120591) ΔV (120591) d120591 + 1003816
100381610038161003816V119905
1003816100381610038161003816
120574minus1V119905= 1198912(119906 V)
(119909 119905) isin Ω times (0 119879)
119906 (119909 119905) = 0 V (119909 119905) = 0
(119909 119905) isin 120597Ω times [0 119879)
119906 (119909 0) = 1199060(119909) 119906
119905(119909 0) = 119906
1(119909) 119909 isin Ω
V (119909 0) = V0(119909) V
119905(119909 0) = V
1(119909) 119909 isin Ω
(9)
was considered by Han and Wang in [20] where Ω is abounded domain with smooth boundary 120597Ω in R119899 119899 =
1 2 3Under suitable assumptions on the functions119892119894 119891119894(119894 =
1 2) the initial data and the parameters in the above problemestablished local existence global existence and blow-upproperty (the initial energy 119864(0) lt 0) This latter blow-upresult has been improved byMessaoudi and Said-Houari [21]into certain solutions with positive initial energy RecentlyLiang and Gao in [22] investigated the following problem
119906119905119905minus Δ119906 + int
119905
0
1198921(119905 minus 120591)Δ119906 (120591) d120591 minus Δ119906
119905= 1198911(119906 V)
(119909 119905) isin Ω times (0 119879)
V119905119905minus ΔV + int
119905
0
1198922(119905 minus 120591)ΔV (120591) d120591 minus ΔV
119905= 1198912(119906 V)
(119909 119905) isin Ω times (0 119879)
(10)
with the same initial and boundary conditions as that of (9)Under suitable assumptions on the functions 119892
119894 119891119894(119894 = 1 2)
Journal of Function Spaces 3
and certain initial data in the stable set they proved that thedecay rate of the solution energy is exponential Converselyfor certain initial data in the unstable set they proved thatthere are solutions with positive initial energy that blow upin finite time It is also worth mentioning the work [23] inwhich we studied system (1) Under suitable assumptions onthe functions 119892
119894 119891119894(119894 = 1 2) and certain initial conditions
we showed that the solutions are global in time and the energydecays exponentially For other papers related to existenceuniform decay and blow-up of solutions of nonlinear waveequations we refer the reader to [14 24ndash29] for existence anduniform decay to [17 30ndash34] for blow-up and to [35ndash40] forthe coupled system To the best of our knowledge the generaldecay and blow-up of solutions for systems of viscoelasticequations of Kirchhoff type with strong damping have notbeen well studied
Motivated by the above mentioned research we con-sider in the present work the coupled system (1) withnonzero 119892
119894(119894 = 1 2) and nonconstant 119872(119904) We note that
in such a coupled system case we should overcome the addi-tional difficulties brought by the treatment of the nonlinearcoupled terms We first establish two blow-up results one isfor certain solutions with nonpositive initial energy as wellas positive initial energy the other is for certain solutionswith arbitrarily positive initial energy Then we give a decayresult of global solutions under a weaker assumption on therelaxation functions 119892
119894(119905) (119894 = 1 2)
This paper is organized as follows In the next section wepresent some assumptions notations and known results andstate the main results Theorems 4 5 6 and 7 The two blow-up results Theorems 5 and 6 are proved in Sections 3 and4 respectively Section 5 is devoted to the proof of the decayresultmdashTheorem 7
2 Preliminaries and Main Result
In this section we present some assumptions notations andknown results and state the main results First we make thefollowing assumptions(A1) 119872(119904) is a positive locally Lipschitz function for 119904 ge
0 with the Lipschitz constant 119871 satisfying
119872(119904) ge 1198980gt 0 (11)
(A2) 119892119894(119905) [0infin) rarr (0infin) (119894 = 1 2) are strictly
decreasing 1198621 functions such that
1198980minus int
infin
0
119892119894(119904) d119904 = 119897
119894gt 0 (12)
(A3) There exist two positive differentiable functions 1205851(119905)
and 1205852(119905) such that
1198921015840
119894(119905) le minus120585
119894(119905) 119892119894(119905) (119894 = 1 2) for 119905 ge 0 (13)
and 120585119894(119905) satisfies
1205851015840
119894(119905) le 0 forall119905 gt 0 int
+infin
0
120585119894(119905) d119905 = infin (119894 = 1 2)
(14)
(A4) We make the following extra assumption on 119872
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904 ge 2 (119901 + 1)1198980119904 forall119904 ge 0 (15)
where 119872(119904) = int
119904
0119872(120591)d120591
Remark 1 It is clear that 119872(119904) = 1198980+ 1198981119904120574 (which occurs
physically in the study of vibrations of damped flexible spacestructures in a bounded domain in R119899) satisfies (A4) for 119904 ge0 1198980gt 0 119898
1ge 0 120574 ge 0 as long as 119901 + 1 gt 120574 Indeed by
straightforward calculations we obtain
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904
= 2 (119901 + 2) (1198980119904 +
1198981
120574 + 1
119904120574+1
) minus 21198980119904 minus 2119898
1119904120574+1
= 2 (119901 + 1)1198980119904 +
2 (119901 + 1 minus 120574)
120574 + 1
1198981119904120574+1
ge 2 (119901 + 1)1198980119904
(16)
Next we introduce some notations Consider
(119892119894 nabla119908) (119905) = int
119905
0
119892119894(119905 minus 119904) nabla119908 (119905) minus nabla119908 (119904)
2
2d119904
119897 = min 1198971 1198972
1198920(119905) = max 119892
1(119905) 1198922(119905) forall119905 ge 0
sdot119902= sdot119871119902(Ω)
1 le 119902 le infin
(17)
the Hilbert space 1198712(Ω) endowed with the inner product
(119906 V) = int
Ω
119906 (119909) V (119909) d119909 (18)
and the functions 1198911(119906 V) and 119891
2(119906 V) (see also [21])
1198911(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901119906|V|119901+2]
1198912(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901+2|V|119901V]
(19)
where 119886 119887 gt 0 are constants and 119901 satisfies
minus 1 lt 119901 if 119899 = 1 2
minus 1 lt 119901 le
(3 minus 119899)
(119899 minus 2)
if 119899 ge 3
(20)
One can easily verify that
1199061198911(119906 V) + V119891
2(119906 V) = 2 (119901 + 2) 119865 (119906 V) forall (119906 V) isin R
2
(21)
where
119865 (119906 V) =1
2 (119901 + 2)
[119886|119906 + V|2(119901+2) + 2119887|119906V|119901+2] (22)
Then we give two lemmas which will be used throughoutthis work
4 Journal of Function Spaces
Lemma 2 (Sobolev-Poincare inequality [41]) If 2 le 120588 le
2119899(119899 minus 2) then
119906120588le 119862nabla119906
2for 119906 isin 119867
1
0(Ω) (23)
holds with some constant 119862
Lemma 3 ([21 Lemma 32]) Assume that (20) holds Thenthere exists 120578
1gt 0 such that for any (119906 V) isin (119867
1
0(Ω) cap
1198672(Ω)) times (119867
1
0(Ω) cap 119867
2(Ω)) one has
119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
le 1205781(1198971nabla1199062
2+ 1198972nablaV22)
119901+2
(24)
We now state a local existence theorem for system (1)whose proof follows the arguments in [3 13]
Theorem 4 Suppose that (20) (1198601) and (1198602) hold andthat 119906
0 V0
isin 1198671
0(Ω) cap 119867
2(Ω) and 119906
1 V1
isin 1198712(Ω) Then
problem (1) has a unique local solution
119906 V isin 119862 ([0 119879) 1198671
0(Ω) cap 119867
2(Ω))
119906119905 V119905isin 119862 ([0 119879) 119871
2(Ω)) cap 119871
2([0 119879) 119867
1
0(Ω))
(25)
for some 119879 gt 0 Moreover at least one of the followingstatements is valid
(1) 119879 = infin
(2) lim119905rarr119879
minus
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ Δ119906
2
2+ ΔV2
2) = infin
(26)
The energy associated with system (1) is given by
119864 (119905) =
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1
2
(int
119905
0
1198921(119904) d119904) nabla119906
2
2
minus
1
2
(int
119905
0
1198922(119904) d119904) nablaV2
2minus int
Ω
119865 (119906 V) d119909
+
1
2
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2
119872(nabla1199062
2) +
1
2
119872(nablaV22) for 119905 ge 0
(27)
As in [5] we can get
1198641015840(119905)
= minus (1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2) minus
1
2
[1198921(119905) nabla119906
2
2+ 1198922(119905) nablaV2
2]
+
1
2
[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)] le 0 forall119905 ge 0
(28)
Then we have
119864 (119905) = 119864 (0) minus int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
minus
1
2
int
119905
0
[1198921(120591) nabla119906 (120591)
2
2+ 1198922(120591) nablaV (120591)2
2] d120591
+
1
2
int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
(29)
We introduce
1198611= 12057812(119901+2)
1 120572
lowast= 119861minus(119901+2)(119901+1)
1
1198641= (
1
2
minus
1
2 (119901 + 2)
)1205722
lowast
(30)
where 1205781is the optimal constant in (24)
Our first result is concerned with the blow-up for certainlocal solutions with nonpositive initial energy as well aspositive initial energy
Theorem 5 Assume that (1198601)-(1198602) (1198604) and (20) hold Let(119906 V) be the unique local solution to system (1) For any fixed120575 lt 1 assuming that we can choose (119906
0 V0) (1199061 V1) satisfy
119864 (0) lt 1205751198641 (119897
1
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (31)
Suppose further that
int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus120575)
2
(119901 + 2) +120575 (1 minus
120575)]
(119894 = 1 2)
(32)
where 120575 = max0 120575 then 119879 lt infin
Our second result shows that certain local solutions witharbitrarily positive initial energy can also blow up
Theorem 6 Suppose that (A1)-(A2) (A4) (20) and
int
infin
0
119892119894(119904) d119904 le
2 (119901 + 1)1198980
2 (119901 + 1) + 12 (119901 + 2)
(119894 = 1 2) (33)
Journal of Function Spaces 5
hold Assume further that 1199060 V0isin 1198671
0(Ω)cap119867
2(Ω) and 119906
1 V1isin
1198712(Ω) and satisfy
0 lt 119864 (0)
lt min
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(34)
then the solution of problem (1) blows up at a finite time 119879lowast inthe sense of (119) belowMoreover the upper bounds for119879lowast canbe estimated by
119879lowastle 2(3119901+5)2(119901+1)
(119901 + 1) 119888
2radic1198861
1 minus [1 + 119888ℎ (0)]minus1(119901+1)
(35)
where ℎ(0) = [11990602
2+ V02
2+ 1198791(nabla11990602
2+ nablaV
02
2)]minus(119901+1)2
and 1198861is given in (116) below
Finally we state the general decay result For conveniencewe choose especially 119872(119904) = 119898
0+ 1198981119904120574 1198980gt 0 119898
1ge 0
and 120574 ge 0 Then the energy functional 119864(119905) defined by (27)becomes
119864 (119905) = 119864 (119906 (119905) V (119905))
=
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(36)
Theorem 7 Suppose that (20) (1198601)-(1198602) and (1198603) holdand that (119906
0 1199061) isin (119867
1
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and (V
0 V1) isin
(1198671
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and satisfy 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (37)
Then for each 1199050gt 0 there exist two positive constants 119870 and
119896 such that the energy of (1) satisfies
119864 (119905) le 119870119890minus119896int119905
1199050120585(119904)d119904
119905 ge 1199050 (38)
where 120585(119905) = min1205851(119905) 1205852(119905)
To achieve general decay result we will use a Lyapunovtype technique for some perturbation energy following themethod introduced in [42] This result improves the one inLi et al [23] in which only the exponential decay rates areconsidered
3 Blow-Up of Solutions with InitialData in the Unstable Set
In this section we prove a finite time blow-up result for initialdata in the unstable set We need the following lemmas
Lemma 8 Suppose that (20) (1198601) (1198602) and (1198604) hold Let(119906 V) be the solution of system (1) Assume further that 119864(0) lt1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (39)
Then there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 for 119905 isin [0 119879) (40)
Proof We first note that by (27) (24) and the definition of1198611 we have
119864 (119905) ge
1
2
(1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+
1
2
(1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1198612(119901+2)
1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
=
1
2
1205722minus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
= 119866 (120572)
(41)
where we have used 119872(119904) = int
119904
0119872(120591)d120591 ge 119898
0119904 ge 0 and
120572 = (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
(42)
It is easy to verify that119866(120572) is increasing in (0 120572lowast) decreasing
in (120572lowastinfin) and that 119866(120572) rarr minusinfin as 120572 rarr infin and
119866(120572)max = 119866 (120572lowast) =
1
2
1205722
lowastminus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
lowast= 1198641 (43)
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Differential EquationsInternational Journal of
Volume 2014
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International Journal of
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Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Discrete Dynamics in Nature and Society
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 3
and certain initial data in the stable set they proved that thedecay rate of the solution energy is exponential Converselyfor certain initial data in the unstable set they proved thatthere are solutions with positive initial energy that blow upin finite time It is also worth mentioning the work [23] inwhich we studied system (1) Under suitable assumptions onthe functions 119892
119894 119891119894(119894 = 1 2) and certain initial conditions
we showed that the solutions are global in time and the energydecays exponentially For other papers related to existenceuniform decay and blow-up of solutions of nonlinear waveequations we refer the reader to [14 24ndash29] for existence anduniform decay to [17 30ndash34] for blow-up and to [35ndash40] forthe coupled system To the best of our knowledge the generaldecay and blow-up of solutions for systems of viscoelasticequations of Kirchhoff type with strong damping have notbeen well studied
Motivated by the above mentioned research we con-sider in the present work the coupled system (1) withnonzero 119892
119894(119894 = 1 2) and nonconstant 119872(119904) We note that
in such a coupled system case we should overcome the addi-tional difficulties brought by the treatment of the nonlinearcoupled terms We first establish two blow-up results one isfor certain solutions with nonpositive initial energy as wellas positive initial energy the other is for certain solutionswith arbitrarily positive initial energy Then we give a decayresult of global solutions under a weaker assumption on therelaxation functions 119892
119894(119905) (119894 = 1 2)
This paper is organized as follows In the next section wepresent some assumptions notations and known results andstate the main results Theorems 4 5 6 and 7 The two blow-up results Theorems 5 and 6 are proved in Sections 3 and4 respectively Section 5 is devoted to the proof of the decayresultmdashTheorem 7
2 Preliminaries and Main Result
In this section we present some assumptions notations andknown results and state the main results First we make thefollowing assumptions(A1) 119872(119904) is a positive locally Lipschitz function for 119904 ge
0 with the Lipschitz constant 119871 satisfying
119872(119904) ge 1198980gt 0 (11)
(A2) 119892119894(119905) [0infin) rarr (0infin) (119894 = 1 2) are strictly
decreasing 1198621 functions such that
1198980minus int
infin
0
119892119894(119904) d119904 = 119897
119894gt 0 (12)
(A3) There exist two positive differentiable functions 1205851(119905)
and 1205852(119905) such that
1198921015840
119894(119905) le minus120585
119894(119905) 119892119894(119905) (119894 = 1 2) for 119905 ge 0 (13)
and 120585119894(119905) satisfies
1205851015840
119894(119905) le 0 forall119905 gt 0 int
+infin
0
120585119894(119905) d119905 = infin (119894 = 1 2)
(14)
(A4) We make the following extra assumption on 119872
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904 ge 2 (119901 + 1)1198980119904 forall119904 ge 0 (15)
where 119872(119904) = int
119904
0119872(120591)d120591
Remark 1 It is clear that 119872(119904) = 1198980+ 1198981119904120574 (which occurs
physically in the study of vibrations of damped flexible spacestructures in a bounded domain in R119899) satisfies (A4) for 119904 ge0 1198980gt 0 119898
1ge 0 120574 ge 0 as long as 119901 + 1 gt 120574 Indeed by
straightforward calculations we obtain
2 (119901 + 2)119872 (119904) minus 2119872 (119904) 119904
= 2 (119901 + 2) (1198980119904 +
1198981
120574 + 1
119904120574+1
) minus 21198980119904 minus 2119898
1119904120574+1
= 2 (119901 + 1)1198980119904 +
2 (119901 + 1 minus 120574)
120574 + 1
1198981119904120574+1
ge 2 (119901 + 1)1198980119904
(16)
Next we introduce some notations Consider
(119892119894 nabla119908) (119905) = int
119905
0
119892119894(119905 minus 119904) nabla119908 (119905) minus nabla119908 (119904)
2
2d119904
119897 = min 1198971 1198972
1198920(119905) = max 119892
1(119905) 1198922(119905) forall119905 ge 0
sdot119902= sdot119871119902(Ω)
1 le 119902 le infin
(17)
the Hilbert space 1198712(Ω) endowed with the inner product
(119906 V) = int
Ω
119906 (119909) V (119909) d119909 (18)
and the functions 1198911(119906 V) and 119891
2(119906 V) (see also [21])
1198911(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901119906|V|119901+2]
1198912(119906 V) = [119886|119906 + V|2(119901+1) (119906 + V) + 119887|119906|
119901+2|V|119901V]
(19)
where 119886 119887 gt 0 are constants and 119901 satisfies
minus 1 lt 119901 if 119899 = 1 2
minus 1 lt 119901 le
(3 minus 119899)
(119899 minus 2)
if 119899 ge 3
(20)
One can easily verify that
1199061198911(119906 V) + V119891
2(119906 V) = 2 (119901 + 2) 119865 (119906 V) forall (119906 V) isin R
2
(21)
where
119865 (119906 V) =1
2 (119901 + 2)
[119886|119906 + V|2(119901+2) + 2119887|119906V|119901+2] (22)
Then we give two lemmas which will be used throughoutthis work
4 Journal of Function Spaces
Lemma 2 (Sobolev-Poincare inequality [41]) If 2 le 120588 le
2119899(119899 minus 2) then
119906120588le 119862nabla119906
2for 119906 isin 119867
1
0(Ω) (23)
holds with some constant 119862
Lemma 3 ([21 Lemma 32]) Assume that (20) holds Thenthere exists 120578
1gt 0 such that for any (119906 V) isin (119867
1
0(Ω) cap
1198672(Ω)) times (119867
1
0(Ω) cap 119867
2(Ω)) one has
119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
le 1205781(1198971nabla1199062
2+ 1198972nablaV22)
119901+2
(24)
We now state a local existence theorem for system (1)whose proof follows the arguments in [3 13]
Theorem 4 Suppose that (20) (1198601) and (1198602) hold andthat 119906
0 V0
isin 1198671
0(Ω) cap 119867
2(Ω) and 119906
1 V1
isin 1198712(Ω) Then
problem (1) has a unique local solution
119906 V isin 119862 ([0 119879) 1198671
0(Ω) cap 119867
2(Ω))
119906119905 V119905isin 119862 ([0 119879) 119871
2(Ω)) cap 119871
2([0 119879) 119867
1
0(Ω))
(25)
for some 119879 gt 0 Moreover at least one of the followingstatements is valid
(1) 119879 = infin
(2) lim119905rarr119879
minus
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ Δ119906
2
2+ ΔV2
2) = infin
(26)
The energy associated with system (1) is given by
119864 (119905) =
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1
2
(int
119905
0
1198921(119904) d119904) nabla119906
2
2
minus
1
2
(int
119905
0
1198922(119904) d119904) nablaV2
2minus int
Ω
119865 (119906 V) d119909
+
1
2
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2
119872(nabla1199062
2) +
1
2
119872(nablaV22) for 119905 ge 0
(27)
As in [5] we can get
1198641015840(119905)
= minus (1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2) minus
1
2
[1198921(119905) nabla119906
2
2+ 1198922(119905) nablaV2
2]
+
1
2
[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)] le 0 forall119905 ge 0
(28)
Then we have
119864 (119905) = 119864 (0) minus int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
minus
1
2
int
119905
0
[1198921(120591) nabla119906 (120591)
2
2+ 1198922(120591) nablaV (120591)2
2] d120591
+
1
2
int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
(29)
We introduce
1198611= 12057812(119901+2)
1 120572
lowast= 119861minus(119901+2)(119901+1)
1
1198641= (
1
2
minus
1
2 (119901 + 2)
)1205722
lowast
(30)
where 1205781is the optimal constant in (24)
Our first result is concerned with the blow-up for certainlocal solutions with nonpositive initial energy as well aspositive initial energy
Theorem 5 Assume that (1198601)-(1198602) (1198604) and (20) hold Let(119906 V) be the unique local solution to system (1) For any fixed120575 lt 1 assuming that we can choose (119906
0 V0) (1199061 V1) satisfy
119864 (0) lt 1205751198641 (119897
1
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (31)
Suppose further that
int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus120575)
2
(119901 + 2) +120575 (1 minus
120575)]
(119894 = 1 2)
(32)
where 120575 = max0 120575 then 119879 lt infin
Our second result shows that certain local solutions witharbitrarily positive initial energy can also blow up
Theorem 6 Suppose that (A1)-(A2) (A4) (20) and
int
infin
0
119892119894(119904) d119904 le
2 (119901 + 1)1198980
2 (119901 + 1) + 12 (119901 + 2)
(119894 = 1 2) (33)
Journal of Function Spaces 5
hold Assume further that 1199060 V0isin 1198671
0(Ω)cap119867
2(Ω) and 119906
1 V1isin
1198712(Ω) and satisfy
0 lt 119864 (0)
lt min
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(34)
then the solution of problem (1) blows up at a finite time 119879lowast inthe sense of (119) belowMoreover the upper bounds for119879lowast canbe estimated by
119879lowastle 2(3119901+5)2(119901+1)
(119901 + 1) 119888
2radic1198861
1 minus [1 + 119888ℎ (0)]minus1(119901+1)
(35)
where ℎ(0) = [11990602
2+ V02
2+ 1198791(nabla11990602
2+ nablaV
02
2)]minus(119901+1)2
and 1198861is given in (116) below
Finally we state the general decay result For conveniencewe choose especially 119872(119904) = 119898
0+ 1198981119904120574 1198980gt 0 119898
1ge 0
and 120574 ge 0 Then the energy functional 119864(119905) defined by (27)becomes
119864 (119905) = 119864 (119906 (119905) V (119905))
=
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(36)
Theorem 7 Suppose that (20) (1198601)-(1198602) and (1198603) holdand that (119906
0 1199061) isin (119867
1
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and (V
0 V1) isin
(1198671
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and satisfy 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (37)
Then for each 1199050gt 0 there exist two positive constants 119870 and
119896 such that the energy of (1) satisfies
119864 (119905) le 119870119890minus119896int119905
1199050120585(119904)d119904
119905 ge 1199050 (38)
where 120585(119905) = min1205851(119905) 1205852(119905)
To achieve general decay result we will use a Lyapunovtype technique for some perturbation energy following themethod introduced in [42] This result improves the one inLi et al [23] in which only the exponential decay rates areconsidered
3 Blow-Up of Solutions with InitialData in the Unstable Set
In this section we prove a finite time blow-up result for initialdata in the unstable set We need the following lemmas
Lemma 8 Suppose that (20) (1198601) (1198602) and (1198604) hold Let(119906 V) be the solution of system (1) Assume further that 119864(0) lt1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (39)
Then there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 for 119905 isin [0 119879) (40)
Proof We first note that by (27) (24) and the definition of1198611 we have
119864 (119905) ge
1
2
(1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+
1
2
(1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1198612(119901+2)
1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
=
1
2
1205722minus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
= 119866 (120572)
(41)
where we have used 119872(119904) = int
119904
0119872(120591)d120591 ge 119898
0119904 ge 0 and
120572 = (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
(42)
It is easy to verify that119866(120572) is increasing in (0 120572lowast) decreasing
in (120572lowastinfin) and that 119866(120572) rarr minusinfin as 120572 rarr infin and
119866(120572)max = 119866 (120572lowast) =
1
2
1205722
lowastminus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
lowast= 1198641 (43)
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
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4 Journal of Function Spaces
Lemma 2 (Sobolev-Poincare inequality [41]) If 2 le 120588 le
2119899(119899 minus 2) then
119906120588le 119862nabla119906
2for 119906 isin 119867
1
0(Ω) (23)
holds with some constant 119862
Lemma 3 ([21 Lemma 32]) Assume that (20) holds Thenthere exists 120578
1gt 0 such that for any (119906 V) isin (119867
1
0(Ω) cap
1198672(Ω)) times (119867
1
0(Ω) cap 119867
2(Ω)) one has
119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
le 1205781(1198971nabla1199062
2+ 1198972nablaV22)
119901+2
(24)
We now state a local existence theorem for system (1)whose proof follows the arguments in [3 13]
Theorem 4 Suppose that (20) (1198601) and (1198602) hold andthat 119906
0 V0
isin 1198671
0(Ω) cap 119867
2(Ω) and 119906
1 V1
isin 1198712(Ω) Then
problem (1) has a unique local solution
119906 V isin 119862 ([0 119879) 1198671
0(Ω) cap 119867
2(Ω))
119906119905 V119905isin 119862 ([0 119879) 119871
2(Ω)) cap 119871
2([0 119879) 119867
1
0(Ω))
(25)
for some 119879 gt 0 Moreover at least one of the followingstatements is valid
(1) 119879 = infin
(2) lim119905rarr119879
minus
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ Δ119906
2
2+ ΔV2
2) = infin
(26)
The energy associated with system (1) is given by
119864 (119905) =
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1
2
(int
119905
0
1198921(119904) d119904) nabla119906
2
2
minus
1
2
(int
119905
0
1198922(119904) d119904) nablaV2
2minus int
Ω
119865 (119906 V) d119909
+
1
2
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2
119872(nabla1199062
2) +
1
2
119872(nablaV22) for 119905 ge 0
(27)
As in [5] we can get
1198641015840(119905)
= minus (1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2) minus
1
2
[1198921(119905) nabla119906
2
2+ 1198922(119905) nablaV2
2]
+
1
2
[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)] le 0 forall119905 ge 0
(28)
Then we have
119864 (119905) = 119864 (0) minus int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
minus
1
2
int
119905
0
[1198921(120591) nabla119906 (120591)
2
2+ 1198922(120591) nablaV (120591)2
2] d120591
+
1
2
int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
(29)
We introduce
1198611= 12057812(119901+2)
1 120572
lowast= 119861minus(119901+2)(119901+1)
1
1198641= (
1
2
minus
1
2 (119901 + 2)
)1205722
lowast
(30)
where 1205781is the optimal constant in (24)
Our first result is concerned with the blow-up for certainlocal solutions with nonpositive initial energy as well aspositive initial energy
Theorem 5 Assume that (1198601)-(1198602) (1198604) and (20) hold Let(119906 V) be the unique local solution to system (1) For any fixed120575 lt 1 assuming that we can choose (119906
0 V0) (1199061 V1) satisfy
119864 (0) lt 1205751198641 (119897
1
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (31)
Suppose further that
int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus120575)
2
(119901 + 2) +120575 (1 minus
120575)]
(119894 = 1 2)
(32)
where 120575 = max0 120575 then 119879 lt infin
Our second result shows that certain local solutions witharbitrarily positive initial energy can also blow up
Theorem 6 Suppose that (A1)-(A2) (A4) (20) and
int
infin
0
119892119894(119904) d119904 le
2 (119901 + 1)1198980
2 (119901 + 1) + 12 (119901 + 2)
(119894 = 1 2) (33)
Journal of Function Spaces 5
hold Assume further that 1199060 V0isin 1198671
0(Ω)cap119867
2(Ω) and 119906
1 V1isin
1198712(Ω) and satisfy
0 lt 119864 (0)
lt min
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(34)
then the solution of problem (1) blows up at a finite time 119879lowast inthe sense of (119) belowMoreover the upper bounds for119879lowast canbe estimated by
119879lowastle 2(3119901+5)2(119901+1)
(119901 + 1) 119888
2radic1198861
1 minus [1 + 119888ℎ (0)]minus1(119901+1)
(35)
where ℎ(0) = [11990602
2+ V02
2+ 1198791(nabla11990602
2+ nablaV
02
2)]minus(119901+1)2
and 1198861is given in (116) below
Finally we state the general decay result For conveniencewe choose especially 119872(119904) = 119898
0+ 1198981119904120574 1198980gt 0 119898
1ge 0
and 120574 ge 0 Then the energy functional 119864(119905) defined by (27)becomes
119864 (119905) = 119864 (119906 (119905) V (119905))
=
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(36)
Theorem 7 Suppose that (20) (1198601)-(1198602) and (1198603) holdand that (119906
0 1199061) isin (119867
1
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and (V
0 V1) isin
(1198671
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and satisfy 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (37)
Then for each 1199050gt 0 there exist two positive constants 119870 and
119896 such that the energy of (1) satisfies
119864 (119905) le 119870119890minus119896int119905
1199050120585(119904)d119904
119905 ge 1199050 (38)
where 120585(119905) = min1205851(119905) 1205852(119905)
To achieve general decay result we will use a Lyapunovtype technique for some perturbation energy following themethod introduced in [42] This result improves the one inLi et al [23] in which only the exponential decay rates areconsidered
3 Blow-Up of Solutions with InitialData in the Unstable Set
In this section we prove a finite time blow-up result for initialdata in the unstable set We need the following lemmas
Lemma 8 Suppose that (20) (1198601) (1198602) and (1198604) hold Let(119906 V) be the solution of system (1) Assume further that 119864(0) lt1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (39)
Then there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 for 119905 isin [0 119879) (40)
Proof We first note that by (27) (24) and the definition of1198611 we have
119864 (119905) ge
1
2
(1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+
1
2
(1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1198612(119901+2)
1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
=
1
2
1205722minus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
= 119866 (120572)
(41)
where we have used 119872(119904) = int
119904
0119872(120591)d120591 ge 119898
0119904 ge 0 and
120572 = (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
(42)
It is easy to verify that119866(120572) is increasing in (0 120572lowast) decreasing
in (120572lowastinfin) and that 119866(120572) rarr minusinfin as 120572 rarr infin and
119866(120572)max = 119866 (120572lowast) =
1
2
1205722
lowastminus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
lowast= 1198641 (43)
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Differential EquationsInternational Journal of
Volume 2014
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Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Stochastic AnalysisInternational Journal of
Journal of Function Spaces 5
hold Assume further that 1199060 V0isin 1198671
0(Ω)cap119867
2(Ω) and 119906
1 V1isin
1198712(Ω) and satisfy
0 lt 119864 (0)
lt min
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(34)
then the solution of problem (1) blows up at a finite time 119879lowast inthe sense of (119) belowMoreover the upper bounds for119879lowast canbe estimated by
119879lowastle 2(3119901+5)2(119901+1)
(119901 + 1) 119888
2radic1198861
1 minus [1 + 119888ℎ (0)]minus1(119901+1)
(35)
where ℎ(0) = [11990602
2+ V02
2+ 1198791(nabla11990602
2+ nablaV
02
2)]minus(119901+1)2
and 1198861is given in (116) below
Finally we state the general decay result For conveniencewe choose especially 119872(119904) = 119898
0+ 1198981119904120574 1198980gt 0 119898
1ge 0
and 120574 ge 0 Then the energy functional 119864(119905) defined by (27)becomes
119864 (119905) = 119864 (119906 (119905) V (119905))
=
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(36)
Theorem 7 Suppose that (20) (1198601)-(1198602) and (1198603) holdand that (119906
0 1199061) isin (119867
1
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and (V
0 V1) isin
(1198671
0(Ω) cap 119867
2(Ω)) times 119871
2(Ω) and satisfy 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (37)
Then for each 1199050gt 0 there exist two positive constants 119870 and
119896 such that the energy of (1) satisfies
119864 (119905) le 119870119890minus119896int119905
1199050120585(119904)d119904
119905 ge 1199050 (38)
where 120585(119905) = min1205851(119905) 1205852(119905)
To achieve general decay result we will use a Lyapunovtype technique for some perturbation energy following themethod introduced in [42] This result improves the one inLi et al [23] in which only the exponential decay rates areconsidered
3 Blow-Up of Solutions with InitialData in the Unstable Set
In this section we prove a finite time blow-up result for initialdata in the unstable set We need the following lemmas
Lemma 8 Suppose that (20) (1198601) (1198602) and (1198604) hold Let(119906 V) be the solution of system (1) Assume further that 119864(0) lt1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (39)
Then there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 for 119905 isin [0 119879) (40)
Proof We first note that by (27) (24) and the definition of1198611 we have
119864 (119905) ge
1
2
(1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+
1
2
(1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1
2 (119901 + 2)
(119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge
1
2
[1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2]
minus
1198612(119901+2)
1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
=
1
2
1205722minus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
= 119866 (120572)
(41)
where we have used 119872(119904) = int
119904
0119872(120591)d120591 ge 119898
0119904 ge 0 and
120572 = (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
(42)
It is easy to verify that119866(120572) is increasing in (0 120572lowast) decreasing
in (120572lowastinfin) and that 119866(120572) rarr minusinfin as 120572 rarr infin and
119866(120572)max = 119866 (120572lowast) =
1
2
1205722
lowastminus
1198612(119901+2)
1
2 (119901 + 2)
1205722(119901+2)
lowast= 1198641 (43)
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
6 Journal of Function Spaces
where 120572lowastis given in (30) Since 119864(0) lt 119864
1 there exists 120572
3gt
120572lowastsuch that 119866(120572
3) = 119864(0) Set 120572
0= (1198971nabla11990602
2+ 1198972nablaV02
2)12
then from (41) we can get 119866(1205720) le 119864(0) = 119866(120572
3) which
implies that 1205720ge 1205723
Now we establish (40) by contradiction First we assumethat (40) is not true over [0 119879) then there exists 119905
0isin (0 119879)
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
lt 1205723 (44)
By the continuity of 1198971nabla119906(119905)
2
2+ 1198972nablaV(119905)2
2we can choose 119905
0
such that
(1198971
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV (1199050)1003817100381710038171003817
2
2)
12
gt 120572lowast (45)
Again the use of (41) leads to
119864 (1199050) ge 119866 [(119897
1
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nabla119906 (1199050)1003817100381710038171003817
2
2)
12
]
gt 119866 (1205723) = 119864 (0)
(46)
This is impossible since 119864(119905) le 119864(0) for all 119905 isin [0 119879)Hence (40) is established
Lemma 9 (see [43 44]) Let 119871(119905) be a positive twice differen-tiable function which satisfies for 119905 gt 0 the inequality
119871 (119905) 11987110158401015840(119905) minus (1 + 120590) 119871
1015840(119905)2ge 0 (47)
for some 120590 gt 0 If 119871(0) gt 0 and 1198711015840(0) gt 0 then there exists a
time 119879lowastle 119871(0)[120590119871
1015840(0)] such that lim
119905rarr119879minus
lowast119871(119905) = infin
Proof of Theorem 5 Assume by contradiction that the solu-tion (119906 V) is global Then we consider 119871(119905) [0 119879] rarr R+
defined by
119871 (119905) = 119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591
+ (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) + 120573(119905 + 119879
0)2
(48)
where 119879 120573 and 1198790are positive constants to be chosen later
Then 119871(119905) gt 0 for all 119905 isin [0 119879] Furthermore
1198711015840(119905) = 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ nabla119906 (119905)2
2+ nablaV (119905)2
2minus (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 2120573 (119905 + 1198790)
= 2int
Ω
119906 (119905) 119906119905(119905) d119909 + 2int
Ω
V (119905) V119905(119905) d119909
+ 2int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+ 2int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591 + 2120573 (119905 + 119879
0)
(49)
and consequently
11987110158401015840(119905) = 2int
Ω
119906 (119905) 119906119905119905(119905) d119909 + 2int
Ω
V (119905) V119905119905(119905) d119909
+ 21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+ 2 (nabla119906 (119905) nabla119906
119905(119905))
+ 2 (nablaV (119905) nablaV119905(119905)) + 2120573
(50)
for almost every 119905 isin [0 119879] Testing the first equation ofsystem (1) with 119906 and the second equation of system (1) withV integrating the results over Ω using integration by partsand summing up we have
(119906119905119905(119905) 119906 (119905)) + (V
119905119905(119905) V (119905)) + (nabla119906 (119905) nabla119906
119905(119905))
+ (nablaV (119905) nablaV119905(119905))
= minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2minus119872(nablaV (119905)2
2) nablaV (119905)2
2
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
(51)
which implies
11987110158401015840(119905) = 2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus 2119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2+ 2120573
minus 2int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
minus 2int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(52)
Therefore we have
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
minus119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Stochastic AnalysisInternational Journal of
Journal of Function Spaces 7
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909) minus 2 (119901 + 3)
times [int
Ω
119906 (119905) 119906119905(119905) d119909 + int
Ω
V (119905) V119905(119905) d119909 + 120573 (119905 + 119879
0)
+ int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
+int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591]
2
= 2119871 (119905) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2minus119872(nabla119906 (119905)
2
2) nabla119906 (119905)
2
2
minus119872(nablaV (119905)22) nablaV (119905)2
2+ 120573)
minus 2119871 (119905) (int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+ int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
minus2 (119901 + 2)int
Ω
119865 (119906 V) d119909)
+ 2 (119901 + 3) 119867 (119905)
minus [119871 (119905) minus (119879 minus 119905) (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
timesΨ (119905)
(53)
where Ψ(119905)119867(119905) [0 119879] rarr R+ are the functions defined by
Ψ (119905) =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
+ int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591 + 120573
119867 (119905) = (119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591 + 120573(119905 + 119879
0)2
)Ψ (119905)
minus [int
Ω
[119906 (119905) 119906119905(119905) + V (119905) V
119905(119905)] d119909
+ int
119905
0
[(nabla119906 (120591) nabla119906119905(120591)) + (nablaV (120591) nablaV
119905(120591))] d120591
+120573 (119905 + 1198790) ]
2
(54)
Using the Cauchy-Schwarz inequality we obtain
(int
Ω
119906 (119905) 119906119905(119905) d119909)
2
le 119906 (119905)2
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
(int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591)
2
le int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905))
int
Ω
119906 (119905) 119906119905(119905) d119909int
Ω
V (119905) V119905(119905) d119909
le 119906 (119905)2
1003817100381710038171003817V119905(119905)
10038171003817100381710038172
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172V (119905)
2
le
1
2
119906 (119905)2
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2V (119905)2
2
(55)
Similarly we have
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
(the similar inequality for V (119905) holds true)
int
Ω
119906 (119905) 119906119905(119905) d119909int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
119906 (119905)2
2int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2int
119905
0
nablaV (120591)22d120591
int
Ω
V (119905) V119905(119905) d119909int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le
1
2
V (119905)22int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2int
119905
0
nabla119906 (120591)2
2d120591
int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591int
119905
0
(nablaV (120591) nablaV119905(120591)) d120591
le
1
2
int
119905
0
nabla119906 (120591)2
2d120591int119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
+
1
2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591int119905
0
nablaV (120591)22d120591
(56)
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Mathematical Problems in Engineering
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Differential EquationsInternational Journal of
Volume 2014
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Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
8 Journal of Function Spaces
By Holderrsquos inequality and Youngrsquos inequality we obtain
120573 (119905 + 1198790) int
Ω
119906 (119905) 119906119905(119905) d119909
le 120573 (119905 + 1198790) 119906 (119905)
2
1003817100381710038171003817119906119905(119905)
10038171003817100381710038172
le
1
2
120573119906 (119905)2
2+
1
2
120573(119905 + 1198790)21003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
(the similar inequality for V (119905) holds true)
120573 (119905 + 1198790) int
119905
0
(nabla119906 (120591) nabla119906119905(120591)) d120591
le 120573 (119905 + 1198790) int
119905
0
nabla119906 (120591)2
1003817100381710038171003817nabla119906119905(120591)
10038171003817100381710038172d120591
le
1
2
120573int
119905
0
nabla119906 (120591)2
2d120591 + 1
2
120573(119905 + 1198790)2
int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
(the similar inequality for V (119905) holds true) (57)
The previous inequalities imply that 119867(119905) ge 0 for every 119905 isin
[0 119879] Using (53) we get
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 119871 (119905)Φ (119905) (58)
for almost every 119905 isin [0 119879] where Φ(119905) [0 119879] rarr R+ is themap defined by
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2(int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
+int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909)
minus 2 (119901 + 2) 120573
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
(59)
For the fourth term on the right hand side of (59) we have
minus int
Ω
int
119905
0
1198921(119905 minus 119904) Δ119906 (119904) 119906 (119905) d119904 d119909
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(60)
Similarly
minus int
Ω
int
119905
0
1198922(119905 minus 119904) ΔV (119904) V (119905) d119904 d119909
= int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) sdot (nablaV (119904) minus nablaV (119905)) d119909 d119904
+ (int
119905
0
1198922(119904) ds) nablaV (119905)2
2
(61)
Combining (59) (60) with (61) we get
Φ (119905) = minus 2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
+ 2int
119905
0
1198921(119904) dsnabla119906 (119905)2
2+ 2int
119905
0
1198922(119904) dsnablaV (119905)2
2
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909 minus 2 (119901 + 2) 120573
+ 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591
+ 2int
119905
0
1198922(119905 minus 119904) int
Ω
nablaV (119905) (nablaV (119904) minus nablaV (119905)) d119909 d119904
minus 2 (119901 + 3)int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591
(62)
Since we have
2int
119905
0
119892119894(119905 minus 119904) int
Ω
nabla119906 (119905) sdot (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
ge minus120576int
119905
0
119892119894(119905 minus 119904) nabla119906 (119904) minus nabla119906 (119905)
2
2d119904
minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2
= minus120576 (119892119894 nabla119906) (119905) minus
1
120576
(int
119905
0
119892119894(119904) d119904) nabla119906 (119905)
2
2 119894 = 1 2
(63)
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
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Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Decision SciencesAdvances in
Discrete MathematicsJournal of
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 9
for any 120576 gt 0 inserting (63) into (62) and utilizing (27) wehave
Φ (119905) ge minus2 (119901 + 2) (1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2)
minus 120576 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ (2 minus
1
120576
)
times [int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2+ int
119905
0
1198922(119904) d119904nablaV (119905)2
2]
minus 2 (119901 + 3) (int
119905
0
1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2d120591 + int
119905
0
1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2d120591)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 2) 120573 minus 4 (119901 + 2) 119864 (119905) + 4 (119901 + 2) 119864 (119905)
= minus4 (119901 + 2) 119864 (119905) + 2 (119901 + 2)119872(nabla119906 (119905)2
2)
minus 2119872(nabla119906 (119905)2
2) nabla119906 (119905)
2
2
+ 2 (119901 + 2)119872(nablaV (119905)22)
minus 2119872(nablaV (119905)22) nablaV (119905)2
2
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198921(119904) d119904nabla119906 (119905)2
2
minus 2 (119901 + 2) 120573
minus 2 (119901 + 1 +
1
2120576
)int
119905
0
1198922(119904) d119904nablaV (119905)2
2
minus 2 (119901 + 3)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(64)
Using (29) and (A4) we have
Φ (119905) ge minus4 (119901 + 2) 119864 (0) + 2 (119901 + 1)
times (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
minus
1
120576
(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ 2 (119901 + 1) (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
minus
1
120576
(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2minus 2 (119901 + 2) 120573
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
= minus4 (119901 + 2) 119864 (0)
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2minus 2 (119901 + 2) 120573
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
120576
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ [2 (119901 + 2) minus 120576] [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(65)
If 120575 lt 0 that is 119864(0) lt 0 we choose 120576 = 2(119901 + 2) in (65)and 120573 small enough such that 120573 le minus2119864(0) Then by (32) wehave
Φ (119905) ge [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
+ [2 (119901 + 1)1198980
minus(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) (minus2119864 (0) minus 120573) ge 0
(66)
If 0 le 120575 lt 1 that is 0 le 119864(0) lt 1205751198641lt 1198641 we choose
120576 = 2(119901 + 2)(1 minus 120575) + 2120575 and 120573 = 2(1205751198641minus 119864(0)) in (65) Then
we get
Φ (119905)
ge minus4 (119901 + 2) 1205751198641
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198921(119904) d119904]
times nabla119906 (119905)2
2
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
10 Journal of Function Spaces
+ [2 (119901 + 1)1198980minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)
times int
119905
0
1198922(119904) d119904]
times nablaV (119905)22
+ 2 (119901 + 1)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 1) 120575 [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(67)
By (32) we have (notice that 120575 = 120575 due to 120575 ge 0)
int
119905
0
119892119894(119904) d119904
le int
infin
0
119892119894(119904) d119904
le
2 (119901 + 1)1198980
2 (119901 + 1) + 1 2 [(1 minus 120575)2(119901 + 2) + 120575 (1 minus 120575)]
=
2 (119901 + 1)1198980minus 2120575 (119901 + 1)119898
0
2 (1 minus 120575) (119901 + 1) + 1 2 (1 minus 120575) (119901 + 2) + 2120575
(119894 = 1 2)
(68)
that is
2120575 (119901 + 1) [1198980minus int
119905
0
119892119894(119904) d119904]
le 2 (119901 + 1)1198980
minus (2 (119901 + 1) +
1
2 (119901 + 2) (1 minus 120575) + 2120575
)int
119905
0
119892119894(119904) d119904
(69)
for 119894 = 1 2 Therefore from the above two inequalities and(A2) we can get
Φ (119905) ge minus 4 (119901 + 2) 1205751198641
+ 2120575 (119901 + 1) (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
(70)
Since
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
gt 120572lowast (71)
by Lemma 8 there exists a constant 1205723gt 120572lowastsuch that
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
12
ge 1205723 (72)
which implies119901 + 1
2 (119901 + 2)
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
ge
119901 + 1
2 (119901 + 2)
1205722
3gt
119901 + 1
2 (119901 + 2)
1205722
lowastgt 1198641
(73)
It follows from (67) and (73) that
Φ (119905) ge 4 (119901 + 2) [1205751198641minus 1205751198641] ge 0 (74)
Therefore by (58) (66) and (74) we obtain
119871 (119905) 11987110158401015840(119905) minus
119901 + 3
2
1198711015840(119905)2ge 0 (75)
for almost every 119905 isin [0 119879] By (49) we then choose 1198790
sufficiently large such that
(119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
gt1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2gt 0
(76)
consequently
1198711015840(0) = 2int
Ω
11990601199061d119909 + 2int
Ω
V0V1d119909 + 2120573119879
0gt 0 (77)
Then by (76) and (77) we choose 119879 large enough so that
119879 gt (10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1205731198792
0)
times ((119901 + 1) (int
Ω
11990601199061d119909 + int
Ω
V0V1d119909 + 120573119879
0)
minus (1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) )
minus1
gt 0
(78)
which ensures that 119879 gt (2(119901+1))(119871(0)1198711015840(0)) As (119901+3)2 gt
1 letting 120590 = (119901 + 1)2 we can select 119879lowastsuch that 119879
lowastle
119871(0)1205901198711015840(0) le 119879 By using Lemma 9 we get lim
119905rarr119879minus
lowast119871(119905) =
infin This implies that
lim119905rarr119879
minus
lowast
(nabla119906 (119905)2
2+ nablaV (119905)2
2) = infin (79)
which is a contradiction Thus 119879 lt infin
4 Blow-Up of Solutions withArbitrarily Positive Initial Energy
In this section we prove the second blow-up result(Theorem 6) for solutions with arbitrarily positive initialenergy In order to attain our aim we need the following threelemmas
Lemma 10 (see [4]) Let 120575lowast gt 0 and 119861(119905) isin 1198622(0infin) be a
nonnegative function satisfying
11986110158401015840(119905) minus 4 (120575
lowast+ 1) 119861
1015840(119905) + 4 (120575
lowast+ 1) 119861 (119905) ge 0 (80)
If
1198611015840(0) gt 119903
2119861 (0) + 119870
0 (81)
then
1198611015840(119905) gt 119870
0(82)
for 119905 gt 0 where 1198700is a constant and 119903
2= 2(120575
lowast+ 1) minus
2radic(120575lowast+ 1)120575lowast is the smallest root of the equation
1199032minus 4 (120575
lowast+ 1) 119903 + 4 (120575
lowast+ 1) = 0 (83)
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 11
Lemma 11 (see [4]) If ℎ(t) is a nonincreasing function on[0infin) and satisfies the differential inequality
ℎ1015840(119905)2ge 119886lowast+ 119887lowastℎ(119905)2+1120575
lowast
for 119905 ge 0 (84)
where 119886lowastgt 0 120575
lowastgt 0 and 119887
lowastgt 0 then there exists a finite
time 119879lowast such that lim119905rarr119879
lowastminusℎ(119905) = 0 and the upper bound of119879lowast is estimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic119886lowast
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(85)
where 119888 = (119886lowast119887lowast)2+1120575
lowast
For the next lemma we define
119870 (119905) = 119870 (119906 (119905) V (119905)) = 119906 (119905)2
2+ V (119905)2
2
+ int
119905
0
nabla119906 (120591)2
2d120591 + int
119905
0
nablaV (120591)22d120591 119905 ge 0
(86)
Lemma 12 Assume that the conditions ofTheorem 6 hold andlet (119906 V) be a solution of (1) then
1198701015840(119905) gt
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 119905 gt 0 (87)
Proof By (86) we have
1198701015840(119905) = 2int
Ω
119906119906119905d119909 + 2int
Ω
VV119905d119909 + nabla119906
2
2+ nablaV2
2 (88)
11987010158401015840(119905) = 2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ 2
1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ 2int
Ω
119906119906119905119905d119909
+ 2int
Ω
VV119905119905d119909 + 2int
Ω
nabla119906 sdot nabla119906119905d119909
+ 2int
Ω
nablaV sdot nablaV119905d119909
(89)
Testing the first equation of system (1) with 119906 and testing thesecond equation of system (1) with V and plugging the resultsinto the expression of11987010158401015840(119905) we obtain
11987010158401015840(119905) = 2 (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus 2119872(nabla119906
2
2) nabla119906
2
2
minus 2119872(nablaV22) nablaV2
2+ 4 (119901 + 2)int
Ω
119865 (119906 V) d119909
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(90)
By (27) (29) and (90) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0)
+ 4 (119901 + 2)int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2) [119872(nabla1199062
2) +119872(nablaV2
2)]
minus [2119872(nabla1199062
2) + 2 (119901 + 2)int
119905
0
1198921(119904) d119904] nabla1199062
2
minus [2119872(nablaV22) + 2 (119901 + 2)int
119905
0
1198922(119904) d119904] nablaV2
2
+ 2 (119901 + 2) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus 2 (119901 + 2)int
119905
0
[(1198921015840
1 nabla119906) (120591) + (119892
1015840
2 nablaV) (120591)] d120591
+ 2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
+ 2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
(91)
By using Holderrsquos inequality and Youngrsquos inequality we have
2int
119905
0
int
Ω
1198921(119905 minus 119904) nabla119906 (119904) sdot nabla119906 (119905) d119909 d119904
= 2int
119905
0
1198921(119905 minus 119904) int
Ω
nabla119906 (119905) (nabla119906 (119904) minus nabla119906 (119905)) d119909 d119904
+ 2 (int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
ge minus2 (119901 + 2) (1198921 nabla119906) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
(92)
Similarly
2int
119905
0
int
Ω
1198922(119905 minus 119904) nablaV (119904) sdot nablaV (119905) d119909 d119904
ge minus2 (119901 + 2) (1198922 nablaV) (119905)
+ (2 minus
1
2 (119901 + 2)
)(int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
(93)
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
12 Journal of Function Spaces
Then taking (92) and (93) into account we obtain
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
+ 2 (119901 + 2)119872(nabla1199062
2)
minus [2119872(nabla1199062
2)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198921(119904) d119904]
timesnabla1199062
2
+ 2 (119901 + 2)119872(nablaV22)
minus [2119872(nablaV22)
+(2 (119901 + 1) +
1
2 (119901 + 2)
)int
119905
0
1198922(119904) d119904]
times nablaV22
(94)
Thus by (A4) and (33) we get
11987010158401015840(119905) minus 2 (119901 + 3) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
ge minus4 (119901 + 2) 119864 (0) + 4 (119901 + 2)
times int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(95)
We note that
nabla119906 (119905)2
2minus1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nabla119906 sdot nabla119906119905d119909 d120591
nablaV (119905)22minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2= 2int
119905
0
int
Ω
nablaV sdot nablaV119905d119909 d120591
(96)
ByHolderrsquos inequality and Youngrsquos inequality we obtain from(96)
nabla119906 (119905)2
2+ nablaV (119905)2
2le1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
+ int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(97)
ByHolderrsquos inequality and Youngrsquos inequality again it followsfrom (86) (88) and (97) that
1198701015840(119905) le 119870 (119905) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
+ int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(98)
In view of (95) and (98) we have
11987010158401015840(119905) minus 2 (119901 + 3)119870
1015840(119905) + 2 (119901 + 3)119870 (119905) + 119871
4ge 0 (99)
where
1198714= 4 (119901 + 2) 119864 (0) + 2 (119901 + 3) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (100)
Let
119861 (119905) = 119870 (119905) +
1198714
2 (119901 + 3)
119905 gt 0 (101)
Then 119861(119905) satisfies (80) for 120575lowast = (119901+1)2 By (81) we see thatif
1198701015840(0) gt (119901 + 3 minus radic(119901 + 3) (119901 + 1)) [119870 (0) +
1198714
2 (119901 + 3)
]
+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2
(102)
that is if
119864 (0) lt
radic119901 + 3
(119901 + 2) (radic119901 + 3 minus radic119901 + 1)
int
Ω
(11990601199061+ V0V1) d119909
minus
119901 + 3
2 (119901 + 2)
(10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
(103)
which is satisfied by the second hypothesis to Theorem 6thenwe get fromLemma 10 that 119870
1015840(119905) gt nabla119906
02
2+nablaV02
2 119905 gt
0 Thus the proof of Lemma 12 is completed
In what follows we find an estimate for the life spanof 119870(119905) and proveTheorem 6
Proof of Theorem 6 Let
ℎ (119905) = [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus120575lowast
for 119905 isin [0 1198791]
(104)
where 120575lowast = (119901 + 1)2 and 1198791gt 0 is a certain constant which
will be specified later Then we have
ℎ1015840(119905) = minus120575
lowastℎ(119905)1+1120575
lowast
(1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2) (105)
ℎ10158401015840(119905) = minus120575
lowastℎ(119905)1+2120575
lowast
119881 (119905) (106)
where
119881 (119905) = 11987010158401015840(119905) [119870 (119905) + (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus (1 + 120575lowast) (1198701015840(119905) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
(107)
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Mathematical Problems in Engineering
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Differential EquationsInternational Journal of
Volume 2014
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Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 13
For simplicity we denote
119875 = 119906 (119905)2
2+ V (119905)2
2
119876 = int
119905
0
(nabla119906 (120591)2
2+ nablaV (120591)2
2) d120591
119877 =1003817100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2+1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
119878 = int
119905
0
(1003817100381710038171003817nabla119906119905(120591)
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905(120591)
1003817100381710038171003817
2
2) d120591
(108)
It follows from (88) (96) Holderrsquos inequality and Youngrsquosinequality that
1198701015840(119905) le 2 (radic119875119877 + radic119876119878) +
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2 (109)
By (95) we get
11987010158401015840(119905) ge (minus4 minus 8120575
lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878) (110)
Applying (107)ndash(110) we obtain
119881 (119905) ge [(minus4 minus 8120575lowast) 119864 (0) + 4 (1 + 120575
lowast) (119877 + 119878)]
times [119870 (119905) + (1198791minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
minus 4 (1 + 120575lowast) (radic119875119877 + radic119876119878)
2
(111)
From (104) and (98) we deduce that
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
+ 4 (1 + 120575lowast) (119877 + 119878) (119879
1minus 119905) (
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
+ 4 (1 + 120575lowast) [(119877 + 119878) (119875 + 119876) minus (radic119875119877 + radic119876119878)
2
]
(112)
By Cauchy-Schwarz inequality the last term in the aboveinequality is nonnegative Hence we have
119881 (119905) ge (minus4 minus 8120575lowast) 119864 (0) ℎ(119905)
minus1120575lowast
119905 ge 0 (113)
Therefore by (106) and (113) we get
ℎ10158401015840(119905) le 120575
lowast(4 + 8120575
lowast) 119864 (0) ℎ(119905)
1+1120575lowast
119905 ge 0 (114)
Note that by Lemma 12 ℎ1015840(119905) lt 0 for 119905 gt 0 Multiplying (114)by ℎ1015840(119905) and integrating from 0 to 119905 we obtain
ℎ1015840(119905)2ge 1198861+ 1198871ℎ(119905)2+1120575
lowast
for 119905 ge 0 (115)
where
1198861= 120575lowast2ℎ(0)2+2120575
lowast
times [(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
minus8119864 (0) ℎ(0)minus1120575lowast
]
(116)
1198871= 8120575lowast2119864 (0) (117)
We observe that 1198861gt 0 if
119864 (0) lt
(1198701015840(0) minus
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2minus1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
2
8 [119870 (0) + 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
=
(int
Ω
11990601199061d119909 + int
Ω
V0V1d119909)2
2 [10038171003817100381710038171199060
1003817100381710038171003817
2
2+1003817100381710038171003817V0
1003817100381710038171003817
2
2+ 1198791(1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)]
(118)
Then by Lemma 11 there exists a finite time 119879lowast such that
lim119905rarr119879
lowastminusℎ(119905) = 0 Moreover the upper bounds of 119879lowast areestimated by
119879lowastle 2(3120575lowast+1)2120575
lowast 120575lowast119888
radic1198861
1 minus [1 + 119888ℎ (0)]minus12120575
lowast
(119)
Therefore
lim119905rarr119879
lowastminus
119870 (119905)
= lim119905rarr119879
lowastminus
(119906 (119905)2
2+ V (119905)2
2+ int
119905
0
nabla119906 (120591)2
2d120591
+int
119905
0
nablaV (120591)22d120591) = infin
(120)
This completes the proof
Remark 13 The choice of1198791in (104) is possible provided that
1198791ge 119879lowast
5 General Decay of Solutions
In this section we prove the general decay of solutions ofsystem (1) The method of proof is similar to that of [42Theorem 35] We first state a lemma which is similar to theone first proved by Vitillaro in [33] to study a class of a scalarwave equation
Lemma 14 ([23 Lemma 32]) Suppose that (20) (A1) and(1198602) hold Let (119906 V) be the solution of system (1) Assumefurther that 119864(0) lt 119864
1and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (121)
Then
(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
12
lt 120572lowast
(122)
for all 119905 isin [0 119879)
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
14 Journal of Function Spaces
The auxiliary functionals 119868(119905) 119869(119905) of problem (1) aredefined as
119868 (119905) = 119868 (119906 (119905) V (119905)) = (1198980minus int
119905
0
1198921(119904) d119904) nabla119906 (119905)
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
119869 (119905) = 119869 (119906 (119905) V (119905))
=
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+
1
2
[ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
+
1198981
120574 + 1
(nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)]
minus int
Ω
119865 (119906 V) d119909
(123)
Lemma 15 Suppose that (20) (A1) and (1198602) hold Let (119906 V)be the solution of system (1) Assume further that 119864(0) lt 119864
1
and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (124)
Then
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2) le
2 (119901 + 2)
119901 + 1
119864 (119905) (125)
(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905) (126)
for all 119905 isin [0 119879)
Proof Since 119864(0) lt 1198641and
(1198971
1003817100381710038171003817nabla1199060
1003817100381710038171003817
2
2+ 1198972
1003817100381710038171003817nablaV0
1003817100381710038171003817
2
2)
12
lt 120572lowast (127)
it follows from Lemma 14 and (30) that
1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
lt 1205722
lowast= 120578minus1(119901+1)
1
(128)
which implies that
119868 (119905) ge (1198980minus int
infin
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
infin
0
1198922(119904) d119904) nablaV2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
= 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus (119886119906 + V2(119901+2)2(119901+2)
+ 2119887119906V119901+2119901+2
)
ge 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+2
= (1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
times [1 minus 1205781(1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2)
119901+1
] ge 0
(129)
for 119905 isin [0 119879) where we have used (24) Further by (123) wehave
119869 (119905) ge
1
2
[(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+ (1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2+ (1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) ]
minus int
Ω
119865 (119906 V) d119909 minus
1
2 (119901 + 2)
119868 (119905) +
1
2 (119901 + 2)
119868 (119905)
ge (
1
2
minus
1
2 (119901 + 2)
)
times [(1198980minus int
119905
0
1198921(119904) d119904) nabla119906
2
2
+(1198980minus int
119905
0
1198922(119904) d119904) nablaV2
2]
+ (
1
2
minus
1
2 (119901 + 2)
) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2 (119901 + 2)
119868 (119905)
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 15
ge
119901 + 1
2 (119901 + 2)
times [1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2
+ (1198921 nabla119906) (119905) + (119892
2 nablaV) (119905) ]
+
1
2 (119901 + 2)
119868 (119905)
ge 0
(130)
From (130) and (36) we deduce that
119897 (nabla119906 (119905)2
2+ nablaV (119905)2
2)
le 1198971nabla119906 (119905)
2
2+ 1198972nablaV (119905)2
2le
2 (119901 + 2)
119901 + 1
119869 (119905)
le
2 (119901 + 2)
119901 + 1
119864 (119905)
(1198921 nabla119906) (119905)
+ (1198922 nablaV) (119905) le
2 (119901 + 2)
119901 + 1
119869 (119905) le
2 (119901 + 2)
119901 + 1
119864 (119905)
(131)
We note that the following functional was introduced in[42]
1198661(119905) = 119864 (119905) + 120576
1120601 (119905) + 120576
2120595 (119905) (132)
where 1205761and 1205762are some positive constants and
120601 (119905) = 1205851(119905) int
Ω
119906 (119905) 119906119905(119905) d119909 + 120585
2(119905) int
Ω
V (119905) V119905(119905) d119909
(133)
120595 (119905) = minus 1205851(119905) int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus 1205852(119905) int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
(134)
Here we use the same functional (132) but choose 120585119894(119905) equiv
1 (119894 = 1 2) in (133) and (134)
Lemma 16 There exist two positive constants 1205731and 120573
2such
that
12057311198661(119905) le 119864 (119905) le 120573
21198661(119905) forall119905 ge 0 (135)
Proof From Holderrsquos inequality Youngrsquos inequalityLemma 2 (36) and (125) we deduce1003816100381610038161003816120601 (119905)
1003816100381610038161003816le 1199062
1003817100381710038171003817119906119905
10038171003817100381710038172
+ V2
1003817100381710038171003817V119905
10038171003817100381710038172
le
1
2
(1199062
2+1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+ V22+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le
1
2
1198622(nabla119906
2
2+ nablaV2
2) +
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
le 1198622 119901 + 2
119897 (119901 + 1)
119864 (119905) + 119864 (119905) = (1 + 1198622 119901 + 2
119897 (119901 + 1)
)119864 (119905)
(136)
Applying Holderrsquos inequality Youngrsquos inequality andLemma 2 again it follows that
int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
le1003817100381710038171003817119906119905
10038171003817100381710038172
times [int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909]12
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
int
Ω
(int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2
+
1
2
(1198980minus 119897) int
Ω
int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904))
2d119904 d119909
le
1
2
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
1 nabla119906) (119905)
(137)
Similarly applying Holderrsquos inequality Youngrsquos inequalityand Lemma 2 again we have
int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
le
1
2
1003817100381710038171003817V119905(119905)
1003817100381710038171003817
2
2+
1
2
1198622(1198980minus 119897) (119892
2 nablaV) (119905)
(138)
It follows from (137) (138) (36) and (126) that
1003816100381610038161003816120595 (119905)
1003816100381610038161003816le
1
2
(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+
1
2
1198622(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le 119864 (119905) +
119901 + 2
119901 + 1
1198622(1198980minus 119897) 119864 (119905)
= (1 +
119901 + 2
119901 + 1
1198622(1198980minus 119897))119864 (119905)
(139)
If we take 1205981and 1205982to be sufficiently small then (135) follows
from (132) (136) and (139)
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
16 Journal of Function Spaces
Lemma 17 Under the conditions ofTheorem 7 the functional120601(119905) defined by (133) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)] nabla1199062
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nablaV22
+
1
4120598
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d 119909
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2) forall120598 gt 0
(140)
Proof By using the equations in (1) and setting 120585119894(119905) equiv 1 (119894 =
1 2) in (133) we easily see that
1206011015840(119905) =
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2+ int
Ω
119906119906119905119905d119909 + int
Ω
VV119905119905d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus119872(nabla1199062
2) nabla119906
2
2minus119872(nablaV2
2) nablaV2
2
+ int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
+ int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
minus int
Ω
nabla119906119905sdot nabla119906d119909 minus int
Ω
nablaV119905sdot nablaVd119909 + 2 (119901 + 2)
times int
Ω
119865 (119906 V) d119909
(141)
By Cauchy-Schwarz inequality and Youngrsquos inequality wehave
int
Ω
nabla119906 (119905) sdot int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904 d119909
le (int
119905
0
1198921(119905 minus 119904) d119904) nabla119906 (119905)
2
2
+ int
Ω
int
119905
0
1198921(119905 minus 119904) |nabla119906 (119905)|
times |nabla119906 (119904) minus nabla119906 (119905)| d119904 d119909 le (1 + 120598) (int
119905
0
1198921(119904) d119904)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) le (1 + 120598) (119898
0minus 119897)
times nabla119906 (119905)2
2+
1
4120598
(1198921 nabla119906) (119905) forall120598 gt 0
(142)
In the same way we can get
int
Ω
nablaV (119905) sdot int119905
0
1198922(119905 minus 119904) nablaV (119904) d119904 d119909
le (1 + 120598) (1198980minus 119897) nablaV (119905)2
2+
1
4120598
(1198922 nablaV) (119905)
(143)
int
Ω
nabla119906119905sdot nabla119906d119909 le
120598
2
nabla1199062
2+
1
2120598
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2 (144)
int
Ω
nablaV119905sdot nablaVd119909 le
120598
2
nablaV22+
1
2120598
1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2 forall120598 gt 0 (145)
Using (141)ndash(145) we obtain
1206011015840(119905) le
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2minus 1198980nabla1199062
2
minus 1198980nablaV22minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ (1 + 120598) (1198980minus 119897) (nabla119906
2
2+ nablaV (119905)2
2)
+
1
4120598
((1198921 nabla119906) (119905) + (119892
2 nablaV) (119905))
+
120598
2
(nabla1199062
2+ nablaV2
2) +
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909
=1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2
minus [119897 minus 120598 (1198980minus 119897 +
1
2
)] nabla1199062
2minus [119897 minus 120598 (119898
0minus 119897 +
1
2
)]
times nablaV22+
1
4120598
(1198921 nabla119906) (119905) +
1
4120598
(1198922 nablaV) (119905)
+
1
2120598
(1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
minus 1198981(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 2 (119901 + 2)int
Ω
119865 (119906 V) d119909 forall120598 gt 0
(146)
So Lemma 17 is established
Lemma 18 Under the conditions ofTheorem 7 the functional120595(119905) defined by (134) (with 120585
119894(119905) equiv 1 (119894 = 1 2)) satisfies
1205951015840(119905) le [120578 (119898
0minus 119897) (3119898
0minus 2119897) + 3119862120578119862
7]
times (nabla1199062
2+ nablaV2
2) + 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+ 1205781198981(1198980minus 119897) (nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ [(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 17
minus
1198920(0)
4120578
1198622[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+ (120578 minus int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905
1003817100381710038171003817
2
2
+ (120578 minus int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905
1003817100381710038171003817
2
2 forall120578 gt 0
(147)
where
1198920(0) = max 119892
1(0) 119892
2(0)
1198626= 1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
1198627= 1198622(2119901+3)
[
2 (119901 + 2)
119897 (119901 + 1)
119864 (0)]
2(p+1)
(148)
Proof By using the equations in (1) and set 120585119894(119905) equiv 1 (119894 =
1 2) in (134) we observe that
1205951015840(119905) = minusint
Ω
119906119905119905(119905) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905119905(119905) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909
minus int
Ω
119906119905(119905) int
119905
0
1198921(119905 minus 119904) 119906
119905(119905) d119904 d119909
minus int
Ω
V119905(119905) int
119905
0
1198922(119905 minus 119904) V
119905(119905) d119904 d119909
= int
Ω
119872(nabla1199062
2) nabla119906 (119905)
sdot int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+ int
Ω
119872(nablaV22) nablaV (119905)
sdot int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909
minus int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
times [int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904] d119909
minus int
Ω
(int
119905
0
1198922(119905 minus 119904) nablaV (119904) d119904)
times [int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904] d119909
+ [int
Ω
nabla119906119905(119905) int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904 d119909
+int
Ω
nablaV119905(119905) int
119905
0
1198922(119905 minus 119904) (nablaV (119905) minus nablaV (119904)) d119904 d119909]
minus [int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
1198912(119906 V) int
119905
0
1198922(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus [int
Ω
119906119905(119905) int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904 d119909
+int
Ω
V119905(119905) int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904 d119909]
minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
= 1198681+ sdot sdot sdot + 119868
7minus (int
119905
0
1198921(119904) d119904) 1003817
100381710038171003817119906119905(119905)
1003817100381710038171003817
2
2
minus (int
119905
0
1198922(119904) d119904) 1003817
100381710038171003817V119905(119905)
1003817100381710038171003817
2
2
(149)
In what follows we will estimate 1198681 119868
7in (149) By Youngrsquos
inequality (A2) and (125) we get
10038161003816100381610038161198681
1003816100381610038161003816le 120578119872(nabla119906
2
2) nabla119906
2
2int
119905
0
1198921(119904) d119904
+
1
4120578
119872(nabla1199062
2) (1198921 nabla119906) (119905)
= 120578 (1198980nabla1199062
2+ 1198981nabla1199062(120574+1)
2) int
119905
0
1198921(119904) d119904
+
1
4120578
(1198980+ 1198981nabla1199062120574
2) (1198921 nabla119906) (119905)
le 120578 (1198980minus 119897) (119898
0nabla1199062
2+ 1198981nabla1199062(120574+1)
2)
+
1
4120578
[1198980+ 1198981(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
120574
] (1198921 nabla119906) (119905)
le 1205781198980(1198980minus 119897) nabla119906
2
2+ 1205781198981(1198980minus 119897) nabla119906
2(120574+1)
2
+
1198626
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(150)
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
18 Journal of Function Spaces
Similarly we have
10038161003816100381610038161198682
1003816100381610038161003816le 1205781198980(1198980minus 119897) nablaV2
2+ 1205781198981(1198980minus 119897) nablaV2(120574+1)
2
+
1198626
4120578
(1198922 nablaV) (119905) forall120578 gt 0
(151)
For 1198683in (149) applying (A2)Holderrsquos inequality andYoungrsquos
inequality we deduce
10038161003816100381610038161198683
1003816100381610038161003816le 120578int
Ω
(int
119905
0
1198921(119905 minus 119904) nabla119906 (119904) d119904)
2
d119909
+
1
4120578
int
Ω
(int
119905
0
1198921(119905 minus 119904) (nabla119906 (119905) minus nabla119906 (119904)) d119904)
2
d119909
le 120578int
Ω
[int
119905
0
1198921(119905 minus 119904) (|nabla119906 (119904) minus nabla119906 (119905)| + |nabla119906 (119905)|) d119904]
2
d119909
+
1
4120578
(1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(int
119905
0
1198921(119904) d119904)
2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905)
le 2120578(1198980minus 119897)2
nabla1199062
2
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
1 nabla119906) (119905) forall120578 gt 0
(152)
Similarly
10038161003816100381610038161198684
1003816100381610038161003816le 2120578(119898
0minus 119897)2
nablaV22
+ (2120578 +
1
4120578
) (1198980minus 119897) (119892
2 nablaV) (119905) forall120578 gt 0
(153)
In the same way we have
10038161003816100381610038161198685
1003816100381610038161003816le 120578 (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1
4120578
(1198980minus 119897) [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(154)
By Youngrsquos inequality Lemma 2 and (125) we see that
10038161003816100381610038161003816100381610038161003816
int
Ω
1198911(119906 V) int
119905
0
1198921(119905 minus 119904) (119906 (119905) minus 119906 (119904)) ds dx
10038161003816100381610038161003816100381610038161003816
le 120578int
Ω
(119886|119906 + V|2119901+3 + 119887|119906|119901+1
|V|119901+2)2
d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578int
Ω
(|119906|2(2119901+3)
+ |V|2(2119901+3) + |119906|2(119901+1)
|V|2(119901+2)) d119909
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 119862120578 [1199062(2119901+3)
2(2119901+3)+ V2(2119901+3)2(2119901+3)
+ 1199062(119901+1)
2(2119901+3)V2(119901+2)2(2119901+3)
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
times [nabla1199062(2119901+3)
2+ nablaV2(2119901+3)
2+ nabla119906
2(119901+1)
2nablaV2(119901+2)2
]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le 1198621205781198622(2119901+3)
(
2 (119901 + 2)
119897 (119901 + 1)
119864 (0))
2119901+2
times [nabla1199062
2+ nablaV2
2+ nabla119906
2nablaV2]
+
1198622(1198980minus 119897)
4120578
(1198921 nabla119906) (119905)
le
3
2
1198621205781198627[nabla119906
2
2+ nablaV2
2]
+
C2 (1198980minus 119897)
4120578
(1198921 nabla119906) (119905) forall120578 gt 0
(155)
Hence we infer that
10038161003816100381610038161198686
1003816100381610038161003816le 3119862120578119862
7(nabla119906
2
2+ nablaV2
2)
+
1198622(1198980minus 119897)
4120578
[(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall120578 gt 0
(156)
By Youngrsquos inequality and Lemma 2 again we obtain
10038161003816100381610038161198687
1003816100381610038161003816le 120578
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
1(119905 minus 119904) (119906 (119905) minus 119906 (119904)) d119904)
2
d119909
+ 1205781003817100381710038171003817V119905
1003817100381710038171003817
2
2+
1
4120578
int
Ω
(int
119905
0
1198921015840
2(119905 minus 119904) (V (119905) minus V (119904)) d119904)
2
d119909
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) +
1198622
4120578
(int
119905
0
1198921015840
1(119904) d119904) (119892
1015840
1 nabla119906) (119905)
+
1198622
4120578
(int
119905
0
1198921015840
2(119904) d119904) (119892
1015840
2 nablaV) (119905)
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 19
le 120578 (1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2) minus
1198921(0) 1198622
4120578
(1198921015840
1 nabla119906) (119905)
minus
1198922(0) 1198622
4120578
(1198921015840
2 nablaV) (119905) forall120578 gt 0
(157)
Combining (149)ndash(157) we complete the proof of Lemma 18
Proof of Theorem 7 Since119892119894are positive we have for any 119905
0gt
0
int
119905
0
119892119894(119904) d119904 ge int
1199050
0
119892119894(119904) d119904 (119894 = 1 2) 119905 ge 119905
0 (158)
denote
1198923= minint
1199050
0
1198921(119904) d119904 int
1199050
0
1198922(119904) d119904 (159)
By using (28) (132) (140) and (147) a series of computationsfor 119905 ge 119905
0 we have
1198661015840
1(119905) = 119864
1015840(119905) + 120576
11206011015840(119905) + 120576
21205951015840(119905)
le minus1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7]
times [nabla1199062
2+ nablaV2
2]
minus [11989811205761minus 11989811205762120578 (1198980minus 119897)]
times (nabla1199062(120574+1)
2+ nablaV2(120574+1)
2)
minus (1 minus
1205761
2120598
minus 1205762120578) (
1003817100381710038171003817nabla119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817nablaV119905
1003817100381710038171003817
2
2)
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
minus (12057621198923minus 1205762120578 minus 1205761) (
1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
+ 21205761(119901 + 2) int
Ω
119865 (119906 V) d119909
+ (
1
2
minus
1198920(0)
4120578
12057621198622)
times [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
(160)
We choose 1205761 1205762 and 120578 small enough such that
1205762120578 (1198980minus 119897) lt 120576
1lt 1205762(1198923minus 120578) (161)
and 120598 = 1205761 then we can check that
1198628= 12057621198923minus 1205762120578 minus 1205761gt 0
11986210
= 11989811205761minus 11989811205762120578 (1198980minus 119897) gt 0
11986211
=
1
2
minus
1198920(0)
4120578
12057621198622gt 0
11986212
= 1 minus
1205761
2120598
minus 1205762120578 gt 0
(162)
We choose 120578 1205761 and 120576
2so small that (162) remains valid and
further
1198629= 1205761[119897 minus 120598 (119898
0minus 119897 +
1
2
)]
minus 1205762120578 [(1198980minus 119897) (3119898
0minus 2119897) + 3119862119862
7] gt 0
(163)
So we arrive at
1198661015840
1(119905) le minus 119862
8(1003817100381710038171003817119906119905
1003817100381710038171003817
2
2+1003817100381710038171003817V119905
1003817100381710038171003817
2
2)
minus 1198629(nabla119906
2
2+ nablaV2
2) + 2120576
1(119901 + 2)int
Ω
119865 (119906 V) d119909
minus 11986210(nabla119906
2(120574+1)
2+ nablaV2(120574+1)
2)
+ 11986211[(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
+
1205761
4120598
+ 1205762[(2120578 +
2 + 1198622
4120578
) (1198980minus 119897) +
1198626
4120578
]
times [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
(164)
which yields (if needed one can choose 1205762sufficiently small)
1198661015840
1(119905) le minus119888
lowast119864 (119905) + 119862 [(119892
1 nabla119906) (119905) + (119892
2 nablaV) (119905)]
forall119905 ge 1199050
(165)
where 119888lowastis some positive constant It follows from (165) (A3)
and (28) that
120585 (119905) 1198661015840
1(119905) le minus119888
lowast120585 (119905) 119864 (119905)
+ 119862120585 (119905) [(1198921 nabla119906) (119905) + (119892
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) + 119862120585
1(119905) (1198921 nabla119906) (119905)
+ 1198621205852(119905) (1198922 nablaV) (119905)
le minus119888lowast120585 (119905) 119864 (119905)
minus 119862 [(1198921015840
1 nabla119906) (119905) + (119892
1015840
2 nablaV) (119905)]
le minus119888lowast120585 (119905) 119864 (119905) minus 119862119864
1015840(119905) forall119905 ge 119905
0
(166)
That is
1198711015840
lowast(119905) le minus119888
lowast120585 (119905) 119864 (119905) le minus119896120585 (119905) 119871
lowast(119905) forall119905 ge 119905
0 (167)
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
20 Journal of Function Spaces
where 119871lowast(119905) = 120585(119905)119866
1(119905) + 119862119864(119905) is equivalent to 119864(119905) due
to (135) and 119896 is a positive constant A simple integration of(167) leads to
119871lowast(119905) le 119871
lowast(1199050) 119890minus119896int119905
1199050120585(119904)d119904
forall119905 ge 1199050 (168)
This completes the proof
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors are grateful to the anonymous referees and theeditors for their useful remarks and comments on an earlyversion of this work This work was partly supported bythe National Natural Science Foundation of China (Grantno 11301277) the Qing Lan Project of Jiangsu Provinceand the Chinese Ministry of Finance Project (Grant noGYHY200906006)
References
[1] R Torrejon and J M Yong ldquoOn a quasilinear wave equationwith memoryrdquo Nonlinear Analysis Theory Methods amp Applica-tions vol 16 no 1 pp 61ndash78 1991
[2] J E Munoz Rivera ldquoGlobal solution on a quasilinear waveequation with memoryrdquo Unione Matematica Italiana B vol 8no 2 pp 289ndash303 1994
[3] S-T Wu and L-Y Tsai ldquoOn global existence and blow-upof solutions for an integro-differential equation with strongdampingrdquo Taiwanese Journal of Mathematics vol 10 no 4 pp979ndash1014 2006
[4] M-R Li and L-Y Tsai ldquoExistence and nonexistence of globalsolutions of some system of semilinear wave equationsrdquoNonlin-ear Analysis Theory Methods amp Applications vol 54 no 8 pp1397ndash1415 2003
[5] S-TWu ldquoExponential energy decay of solutions for an integro-differential equation with strong dampingrdquo Journal of Mathe-matical Analysis and Applications vol 364 no 2 pp 609ndash6172010
[6] T Matsuyama and R Ikehata ldquoOn global solutions and energydecay for the wave equations of Kirchhoff type with nonlineardamping termsrdquo Journal of Mathematical Analysis and Applica-tions vol 204 no 3 pp 729ndash753 1996
[7] K Ono ldquoBlowing up and global existence of solutions for somedegenerate nonlinear wave equations with some dissipationrdquoNonlinear Analysis Theory Methods amp Applications vol 30 no7 pp 4449ndash4457 1997
[8] K Ono ldquoGlobal existence decay and blowup of solutions forsome mildly degenerate nonlinear Kirchhoff stringsrdquo Journal ofDifferential Equations vol 137 no 2 pp 273ndash301 1997
[9] K Ono ldquoOn global existence asymptotic stability and blowingup of solutions for some degenerate non-linear wave equationsof Kirchhoff type with a strong dissipationrdquo MathematicalMethods in the Applied Sciences vol 20 no 2 pp 151ndash177 1997
[10] K Ono ldquoOn global solutions and blow-up solutions of non-linear Kirchhoff strings with nonlinear dissipationrdquo Journal of
Mathematical Analysis and Applications vol 216 no 1 pp 321ndash342 1997
[11] J Y Park and J J Bae ldquoOn existence of solutions of nondegen-erate wave equations with nonlinear damping termsrdquo NihonkaiMathematical Journal vol 9 no 1 pp 27ndash46 1998
[12] A Benaissa and S A Messaoudi ldquoBlow-up of solutions forthe Kirchhoff equation of 119902-Laplacian type with nonlineardissipationrdquo Colloquium Mathematicum vol 94 no 1 pp 103ndash109 2002
[13] S-T Wu and L-Y Tsai ldquoOn a system of nonlinear waveequations of Kirchhoff type with a strong dissipationrdquo TamkangJournal of Mathematics vol 38 no 1 pp 1ndash20 2007
[14] MM Cavalcanti V N Domingos Cavalcanti and J A SorianoldquoExponential decay for the solution of semilinear viscoelasticwave equations with localized dampingrdquo Electronic Journal ofDifferential Equations vol 2002 no 44 14 pages 2002
[15] E Zuazua ldquoExponential decay for the semilinear wave equationwith locally distributed dampingrdquo Communications in PartialDifferential Equations vol 15 no 2 pp 205ndash235 1990
[16] M M Cavalcanti and H P Oquendo ldquoFrictional versus vis-coelastic damping in a semilinear wave equationrdquo SIAM Journalon Control and Optimization vol 42 no 4 pp 1310ndash1324 2003
[17] S A Messaoudi ldquoBlow up and global existence in a nonlinearviscoelastic wave equationrdquo Mathematische Nachrichten vol260 pp 58ndash66 2003
[18] S A Messaoudi ldquoBlow-up of positive-initial-energy solutionsof a nonlinear viscoelastic hyperbolic equationrdquo Journal ofMathematical Analysis andApplications vol 320 no 2 pp 902ndash915 2006
[19] W Liu ldquoGlobal existence asymptotic behavior and blow-up ofsolutions for a viscoelastic equation with strong damping andnonlinear sourcerdquo Topological Methods in Nonlinear Analysisvol 36 no 1 pp 153ndash178 2010
[20] X Han and M Wang ldquoGlobal existence and blow-up ofsolutions for a system of nonlinear viscoelastic wave equationswith damping and sourcerdquoNonlinear Analysis Theory Methodsamp Applications vol 71 no 11 pp 5427ndash5450 2009
[21] S A Messaoudi and B Said-Houari ldquoGlobal nonexistenceof positive initial-energy solutions of a system of nonlinearviscoelastic wave equations with damping and source termsrdquoJournal of Mathematical Analysis and Applications vol 365 no1 pp 277ndash287 2010
[22] F Liang and H Gao ldquoExponential energy decay and blow-up of solutions for a system of nonlinear viscoelastic waveequations with strong dampingrdquo Boundary Value Problems vol2011 article 22 19 pages 2011
[23] G Li L Hong and W Liu ldquoExponential energy decay of solu-tions for a system of viscoelastic wave equations of Kirchhofftype with strong dampingrdquo Applicable Analysis vol 92 no 5pp 1046ndash1062 2013
[24] D Andrade and L H Fatori ldquoThe nonlinear transmissionproblem with memoryrdquo Boletim da Sociedade Paranaense deMatematica vol 22 no 1 pp 106ndash118 2004
[25] M M Cavalcanti V N Domingos Cavalcanti J S PratesFilho and J A Soriano ldquoExistence and exponential decay for aKirchhoff-Carrier model with viscosityrdquo Journal of Mathemati-cal Analysis and Applications vol 226 no 1 pp 40ndash60 1998
[26] M M Cavalcanti V N Domingos Cavalcanti and M LSantos ldquoExistence and uniform decay rates of solutions to adegenerate system with memory conditions at the boundaryrdquoApplied Mathematics and Computation vol 150 no 2 pp 439ndash465 2004
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Journal of Function Spaces 21
[27] V Komornik Exact Controllability and Stabilization Researchin Applied Mathematics Masson Paris France 1994
[28] W Liu ldquoGeneral decay rate estimate for a viscoelastic equationwith weakly nonlinear time-dependent dissipation and sourcetermsrdquo Journal of Mathematical Physics vol 50 no 11 ArticleID 113506 17 pages 2009
[29] J Y Park and J J Bae ldquoVariational inequality for quasilinearwave equations with nonlinear damping termsrdquo NonlinearAnalysis Theory Methods amp Applications vol 50 no 8 pp1065ndash1083 2002
[30] W Liu ldquoGeneral decay and blow-up of solution for a quasilinearviscoelastic problemwith nonlinear sourcerdquoNonlinearAnalysisTheory Methods amp Applications vol 73 no 6 pp 1890ndash19042010
[31] W Liu and J Yu ldquoOn decay and blow-up of the solution for aviscoelastic wave equation with boundary damping and sourcetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol74 no 6 pp 2175ndash2190 2011
[32] B Said-Houari ldquoGlobal nonexistence of positive initial-energysolutions of a system of nonlinear wave equations with dampingand source termsrdquo Differential and Integral Equations vol 23no 1-2 pp 79ndash92 2010
[33] E Vitillaro ldquoGlobal nonexistence theorems for a class of evolu-tion equations with dissipationrdquo Archive for Rational Mechanicsand Analysis vol 149 no 2 pp 155ndash182 1999
[34] S-T Wu ldquoBlow-up of solutions for a system of nonlinearwave equations with nonlinear dampingrdquo Electronic Journal ofDifferential Equations vol 2009 no 105 11 pages 2009
[35] K Agre and M A Rammaha ldquoSystems of nonlinear waveequations with damping and source termsrdquo Differential andIntegral Equations vol 19 no 11 pp 1235ndash1270 2006
[36] M-R Li and L-Y Tsai ldquoOn a system of nonlinear waveequationsrdquo Taiwanese Journal of Mathematics vol 7 no 4 pp557ndash573 2003
[37] W Liu ldquoUniform decay of solutions for a quasilinear system ofviscoelastic equationsrdquo Nonlinear Analysis Theory Methods ampApplications vol 71 no 5-6 pp 2257ndash2267 2009
[38] F Sun and M Wang ldquoGlobal and blow-up solutions fora system of nonlinear hyperbolic equations with dissipativetermsrdquoNonlinear AnalysisTheory Methods amp Applications vol64 no 4 pp 739ndash761 2006
[39] S-T Wu ldquoOn decay and blow-up of solutions for a system ofnonlinear wave equationsrdquo Journal of Mathematical Analysisand Applications vol 394 no 1 pp 360ndash377 2012
[40] S Yu ldquoPolynomial stability of solutions for a system of non-linear viscoelastic equationsrdquo Applicable Analysis vol 88 no 7pp 1039ndash1051 2009
[41] R A Adams Sobolev Spaces vol 65 of Pure and AppliedMathematics Academic Press New York NY USA 1975
[42] S A Messaoudi ldquoGeneral decay of the solution energy ina viscoelastic equation with a nonlinear sourcerdquo NonlinearAnalysis Theory Methods amp Applications vol 69 no 8 pp2589ndash2598 2008
[43] H A Levine ldquoSome nonexistence and instability theorems forsolutions of formally parabolic equations of the form 119875119906
119905119905=
minus119860119906 +F(119906)rdquo Archive for Rational Mechanics and Analysis vol51 pp 371ndash386 1973
[44] H A Levine ldquoInstability and nonexistence of global solutionsto nonlinear wave equations of the form 119875119906
119905119905= minus119860119906 + F(119906)rdquo
Transactions of the American Mathematical Society vol 192 pp1ndash21 1974
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical Problems in Engineering
Hindawi Publishing Corporationhttpwwwhindawicom
Differential EquationsInternational Journal of
Volume 2014
Applied MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Mathematical PhysicsAdvances in
Complex AnalysisJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
OptimizationJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Operations ResearchAdvances in
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Function Spaces
Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of Mathematics and Mathematical Sciences
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Algebra
Discrete Dynamics in Nature and Society
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Decision SciencesAdvances in
Discrete MathematicsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom
Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Stochastic AnalysisInternational Journal of