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2010 2010I

S

S

U

ISSUE- 4 2010

EDITORIAL BOARD

(i) Dr. R. V. SARAYKAR, Editor - in - Chief,

(Professor, Deptt. of Mathematics, P.G.T.D., Nagpur University)Tel. : 0712 - 3098790 (R), 09890641953 (mobile)e-mail : [email protected]

(ii) Mr. A. S. MUKTIBODH, Associate Editor,

(H. O. D. Mathematics, Mohota Science College, Nagpur)Tel. : 0712 - 2292290, 09850411871 (mobile)e-mail : [email protected]

(iii) Mrs. USHRI DATTA,

(ex-Vice Principal and H.O.D. Mathematics, Hislop College, Nagpur)Tel. : 0712 - 2539434 (R), 09373101518 (mobile)e-mail : [email protected]

(iv) Dr. S. H. GHATE,

(Reader, Deptt, of Mathematics, P.G.T.D., Nagpur University)Tel. : 0712 - 2570690, 09373100997 (mobile)e-mail : [email protected]

(v) Dr. R. K. GUPTA,

(retd. Reader. Deptt. of Mathematics, Nagpur University)Tel. : 0712 - 2573374

(vi) Dr. M. N. DESHPANDE,

(ex-Director, Institute of Science, Nagpur)Tel. : 0712 - 2292745e-mail : [email protected]

(vii) Dr. S. D. MOHGAONKAR,

(Asst. Professor and H.O.D. Mathematics, Ramdeobaba Engineering College Nagpur)Tel. : 0712 - 2539434 (R), 09373101518 (mobile)e-mail : [email protected]

(viii) Dr. V. G. JOSHI,

(retd. H.O.D. Mathematics, Dharampeth College, Nagpur)Tel. : 0712 - 2283313 (R),

Price : Rs. 100/-

(

2233588 9890911449

[email protected]

Professor and HOD, Mathematics, Shri.Ramdeobaba Kamla Nehru Engineering College, Nagpur-13

NUMTA BULLETIN, 2008 ISSN 0974-1623

NUMTA BULLETIN

Edited by

NAGPUR UINIVERSITY MATHEMATICS TEACHERS’ASSOCIATION(NUMTA)

2010

In association with

Shri. Ramdeobaba Kamla Nehru Engineering College, Nagpur-13

Published by

Published by

NUMTA BULLETIN

We the ‘Nagpur University Mathematics Teachers’ Association’

NUMTA , Nagpur , is a self financed, registered organization working for the cause of

Mathematics for the last 12 years. We have been striving to popularize mathematics in

Vidarbha region. We are working towards raising overall standard of mathematics in our

region by organizing various academics programs like Seminars, Workshops, Quiz contests,

Exhibitions , Lecture series etc.

In order to motivate students and teachers to pursue quality research in

mathematics we annually publish a research bulletin ‘NUMTA BULLETIN’. Through this

bulletin we publish genuine articles in pure and applied mathematics.

Due to financial constraints, day by day, it is becoming impossible for

NUMTA to bear the cost ( Rs.20.000) of printing this bulletin.

We, hereby, fervently appeal to all the mathematics loving community to

donate generously towards the publication cost and be a part of our mission to popularize

mathematics and serve the society for the betterment of future generations.

Please contact any one of us at the e-mail address.

Prof. A.S.Muktibodh Prof. Rishi Agrawal

President Secretary

NUMTA NUMTA

[email protected]

APPEAL

allallallallallallallall

AssociationAssociation'

Appeal

[email protected]@yahoo.com

yrs. We at NUMTA areWe at NUMTA are striving to popularize mathematics in theWe at NUMTA are striving to popularize mathematics in theWe at NUMTA are striving to popularize mathematics in the

academic

EDITOR’S WRITE We are extremely happy to bring out this fourth issue of NUMTA BULLETIN. We are thankful to the Mathematical community for their overwhelming response to this project. It is for the benefit of all mathematicians; students, teachers and researchers that we also publish an e-version of NUMTA BULLETIN. You can e-mail to any one from the Editorial Board to procure e-NUMTA BULLETIN. This issue contains articles right from Modern mathematics, like Category Theory to the ones from ancient Indian mathematics. Articles are well- studied and reflect good efforts on the part of the authors. We hope that our learned readers will continue to contribute informative and genuine articles for the Bulletin. We would like to thank Shri.Ramdeobaba Kamla Nehru Engineering College, Nagpur-13 , for the generous support in bringing out this issue of NUMTA BULLETIN.

i

ii

Contents

1. Temıto.pe. Gbo. lahan Jaıyeo. la : On the Factor Set of Code Loops 1-16

2. Kumbhojkar H. V. : Mathematics: Brother of Humor 17-32

3. Muktibodh P. S.: Problems of standard Model in Cosmology 33-51

4. Shobhane A. R. and Vyawahare A.W. : Some Pythagorian Triples

and their Properties 52-57

5. Surendran K. K. : The Realm of Energy and Elementary Particles 58-79

6. Vyawahare A.W. : Madhava’s Contribution to Mathematics 80-97

D.T.P. Work Using LATEX by :

A.S.Muktibodh,

179, Sahakarnagar, (Khmala)

Nagpur-440025

Ph.(0712)2292290

Unity in Mathematics 1-23

Beyond Farey Fibonacci Sequence24-30

Mathematics: Brother of Humor (Contd.) 31-39

Magical Geometrical Figures40-44

Relationship between code loops and some other loops5 45-525.

6. Conformal Killing Vectors in Spherically Symmetric,Conformal Killing Vectors in Spherically Symmetric,

Inhomogeneous, Shear-free, Separable Metric

Spacetimes

Conformal Killing Vectors in Spherically Symmetric,

Inhomogeneous, Shear-free, Separable Metric

Spacetimes

Conformal Killing Vectors in Spherically Symmetric,

Inhomogeneous, Shear-free, Separable Metric

Spacetimes

Conformal Killing Vectors in Spherically Symmetric,

Inhomogeneous, Shear-free, Separable Metric

Spacetimes

53-67

77. Integrated approach and Trace of Ancient

Tradition in SREDHIVYAVHARASredhivyavhara

68-91

8. Ganit- Sar-Sangraha of Mahaviracharya 92-95

: Sanjay Wagh

Kiran SisodiaKiran Sisodia

H.V.Kumbhojkar:

:

: A.W.Vyawahare

: Jayeola Temitope

: S.M.Wagh, R.V.Saraykar, P.S.Muktibodh, K.S.Govinder

: V.D.Heroor

: A.W.Vyawahare

Kiran Sisodia

Jaiyeola Temitope

Relationship between code loops and some other loops ∗†

Temıto.pe. Gbo. lahan Jaıyeo. la‡

Department of Mathematics,Obafemi Awolowo University, Ile Ife, Nigeria.

[email protected], [email protected]

Abstract

Necessary and sufficient conditions for a code loop L(φ) on a binary linear code Cthat is doubly even with a factor set φ to be an homogenoeus loop, a Kikkawa loop, a K-loop and a cross inverse property loop are established. If c(u, v, w) represent the numberof corresponding co-ordinates of code words u, v and w that are non-zero and u·v denotethe number of the corresponding co-ordinates of code words u and v that are non-zero,then it is shown that; c(u, v, x + y) ≡ [c(u, v, x) + c(u, v, y)] mod 2, c(x + y, u, v) ≡[c(x, u, v) + c(y, u, v)] mod 2 and u·x+u·y

2 ≡ u·(x+y)2 mod 2 whenever L(φ) is an A-loop.

1 Introduction

Let L be a loop and Z ≤ Z(L). If L/Z ∼= C where C is an abelian group then, L ∼= L(φ)where φ : C × C → F , F been a field and L(φ) = F × C with binary operation ∗ suchthat for all (a, u), (b, v) ∈ L(φ) ;

(a, u) ∗ (b, v) = (a + b + φ(u, v), u + v) (1)

and (L(φ), ∗) is a loop. The fact that (L(φ), ∗) is a loop is shown in [14].Let V be a finite dimensional vector space over the field F and C ≤ V . With |F | = 2

such that F = ZZ2 = {0, 1}, C is called a binary linear code and its elements (vectors) arecalled code words. For all u, v ∈ C, let ||u|| denote the number of non-zero co-ordinates in u(this is simply equal to the ’norm squared’ of u if V = IRn), let u ·v denote the number of thecorresponding co-ordinates of u and v that are non-zero (this is simply equal to the ’innerproduct’ of u and v if V = IRn) and let c(u, v, w) represent the number of correspondingco-ordinates of u, v and w that are non-zero.

C is called a double even code if :

∗2000 Mathematics Subject Classification. Primary 20NO5.†Keywords : code loop, binary linear code, A-loop, homogeneous loop, Kikkawa loop, K-loop‡All correspondence to be addressed to this author.

1

NUMTA BULLETIN,2010, 45-52NUMTA BULLETIN, 2010, 45-52

45

1. u · v is even

2. ||u|| is divisible by 4.

φ is called a factor set on C if it satisfy the conditions :

φ(u, u) ≡ ||u||4

mod 2 (2)

φ(u, v) + φ(v, u) ≡ u · v2

mod 2 (3)

φ(u, v) + φ(u + v, w) + φ(v, w) + φ(u, v + w) ≡ c(u, v, w) mod 2 (4)

As mentioned in [4], for all u ∈ C, φ(u, 0) = φ(0, u) = 0.For more on the varieties of loops, definitions and their general properties, readers can

check [1],[2], [3], [7] and [13].Code loops were first shown to be Moufang loops by Griess [8] and was later shown to

be Moufang loops with unique non-identity square in [5]. They have also been of interest toChein and Goodaire [6] and P. Vojtechovsky [10], [11], [12] and [14]. Here we shall approachthem in the style of [5].

Necessary and sufficient conditions for a code loop L(φ) on a binary linear code C thatis doubly even with a factor set φ to be an homogenoeus loop, a Kikkawa loop, a K-loopand a cross inverse property loop are established. It is shown that

c(u, v, x+y) ≡ [c(u, v, x)+ c(u, v, y)] mod 2, c(x+y, u, v) ≡ [c(x, u, v)+ c(y, u, v)] mod 2

andu · x + u · y

2≡ u · (x + y)

2mod 2 ∀ u, v, x, y ∈ C

whenever L(φ) is an A-loop.The following definitions are needed. In all, LIPL, RIPL, IPL and AIPL mean a left

inverse property loop, right inverse property loop, inverse property loop and automorphicinverse property loop respectively.

Definition 1.1 Let (G, ◦) be a loop.

1. G is called an Aλ(Aρ,Aµ)-loop if and only if all left(right,middle) inner mappings in Gare automorphisms. It is called an A-loop if and only if it is an Aλ-loop, an Aρ-loopand an Aµ-loop

2. G is called a left(right) homogeneous loop if and only if it is an Aλ(Aρ)-loop and aLIPL(RIPL). It is called an homogeneous loop if and only if it is an A-loop and anIPL.

3. G is called a left(right) K-loop loop if and only if it is a left(right) Bol loop and anAIPL It is called a K-loop if and only if it is a Moufang loop and an AIPL.

4. G is called a left(right) Kikkawa loop if and only if it is a left(right) homogeneous loopand an AIPL. It is called a Kikkawa loop if and only if it is an homogeneous loop andan AI PL.

The automorphism group of a loop (G, ◦) is represented by A(G, ◦) = A(G).

2

T. Jaiyeola 46

Main Results

2 A-Loops And Code Loops

Theorem 2.1 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. If

A(u, v, w) = φ(u, v) + φ(u, v + w) + φ(u + v, w) + φ(v, w) and F (u, v) = φ(u, v) + φ(v, u),then

1. L(φ) is an Aλ-loop ⇔ A(u, v, x + y) = A(u, v, x) + A(u, v, y).

2. L(φ) is an Aρ-loop ⇔ A(x + y, v, u) = A(x, v, u) + A(y, v, u).

3. L(φ) is an Aµ-loop ⇔ F (u, x + y) = F (u, x) + F (u, y).

ProofLet α = (a, u), β = (b, v), γ = (c, x), δ = (d, y) ∈ L(φ).

1. Consider L(α, β) = LαLβL−1βα. Lβα = L(a+b+φ(v,u),u+v). γLβα = (a + b + c + φ(v, u) +

φ(u + v, x), u + v + x) ⇔ (a + b + c + φ(v, u) + φ(u + v, x), u + v + x)L−1βα = γ = (c, x).

L(φ) is an Aλ-loop ⇔ L(α, β) ∈ A(L(φ)) ∀ α, β ∈ L(φ) ⇔ (γδ)L(α, β) =γL(α, β) ∗ δL(α, β) ⇔ (γδ)LαLβL−1

βα = γLαLβL−1βα ∗ δLαLβL−1

βα.

L. H. S.= (γδ)LαLβL−1βα = (a+ b+ c+d+φ(x, y)+φ(u, x+ y)+φ(v, u+x+ y), u+ v +

x + y)L−1βα = (a + b + c + d + φ(v, u) + φ(v, x + y + u) + φ(u + v, x + y) + φ(u, x + y) +

φ(x, y)+φ(v, u)+φ(u+v, x+y), u+v+x+y)L−1βα = (a+b+c+d+φ(x, y)+A(v, u, x+

y)+φ(v, u)+φ(u+v, x+y), u+v +x+y)L−1βα = (c+d+A(v, u, x+y)+φ(x, y), x+y).

R. H. S.= γLαLβL−1βα ∗δLαLβL−1

βα = (a+c+b+φ(u, x)+φ(v, u+x), u+x+v)L−1βα ∗(a+

d+b+φ(u, y)+φ(v, u+y), u+y+v)L−1βα = (a+b+c+φ(v, u)+φ(v, u+x)+φ(v+u, x)+

φ(u, x) + φ(v, u) + φ(u + v, x), u + x + v)L−1βα ∗ (a + d + b + φ(v, u) + φ(v, u + y) + φ(v +

u, y) +φ(u, y) +φ(v, u) +φ(u + v, y), u+ y + v)L−1βα = (a+ b+ c+ A(v, u, x) +φ(v, u) +

φ(u+v, x), u+v +x)L−1βα ∗ (a+ b+d+A(v, u, y)+φ(v, u)+φ(u+v, y), u+v +y)L−1

βα =(c + A(v, u, x), x) ∗ (d + A(v, u, y), y) = (c + d + A(v, u, x) + A(v, u, y) + φ(x, y), x + y).

L(φ) is an Aλ-loop ⇔ L. H. S.=R. H. S. ⇔ A(v, u, x + y) = A(v, u, x) + A(v, u, y).

2. L(φ) is an Aρ-loop ⇔ R(α, β) ∈ A(L(φ)) ∀ α, β ∈ L(φ) ⇔ (γδ)R(α, β) =γR(α, β) ∗ δR(α, β) ⇔ (γδ)RαRβR−1

αβ = γRαRβR−1αβ ∗ δRαRβR−1

αβ .

3

Code Loops and Some Other Loops 47

L. H. S.= (γδ)RαRβR−1αβ = (c+d+a+ b+φ(x, y)+φ(x+y, u)+φ(x+y +u, v), x+y +

u + v)R−1αβ = (a + b + c + d + φ(x + y, u) + φ(x + y, u + v) + φ(x + y + u, v) + φ(u, v) +

φ(u, v) + φ(x + y, u + v) + φ(x, y), x + y + u + v)R−1αβ = (a + b + c + d + A(x + y, u, v) +

φ(x, y)+φ(u, v)+φ(x+y, u+v), x+y+u+v)R−1αβ = (c+d+A(x+y, u, v)+φ(x, y), x+y).

R. H. S.= γRαRβR−1αβ ∗ δRαRβR−1

αβ = (c + a + b + φ(x, u) + φ(x + u, v), x + u + v)R−1αβ ∗

(d+a+b+φ(y, u)+φ(y+u, v), y+u+v)R−1αβ = (a+b+c+φ(x, u)+φ(x, u+v)+φ(x+

u, v)+φ(u, v)+φ(u, v)+φ(x, u+v), u+v+x)R−1αβ ∗(a+b+d+φ(y, u)+φ(y, u+v)+φ(y+

u, v)+φ(u, v)+φ(u, v)+φ(y, u+ v), u+ v + y)R−1αβ = (a+ b+ c+A(x, u, v)+φ(u, v)+

φ(x, u+v), u+v +x)R−1αβ ∗ (a+ b+d+A(y, u, v)+φ(u, v)+φ(y, u+v), u+v +y)R−1

αβ =(c + A(x, u, v), x) ∗ (d + A(y, u, v), y) = (c + d + A(x, u, v) + A(y, u, v) + φ(x, y), x + y).

L(φ) is an Aρ-loop ⇔ L. H. S. =R. H. S. ⇔ A(x + y, v, u) = A(x, v, u) + A(y, v, u).

3. Consider Tα = RαL−1α . γLα = (a + c + φ(u, x), u + x) ⇔ (a + c + φ(u, x), u + x)L−1

α =(c, x).

L(φ) is an Aµ-loop ⇔ (γδ)Tα = γTα ∗ δTα.

L. H. S. = (γδ)Tα = (c + d + a + φ(x, y) + φ(x + y, u), x + y + u)L−1α =

(c + d + a + φ(u, x + y) + φ(x + y, u) + φ(u, x + y) + φ(x, y), x + y + u)L−1α = (a + c +

d+F (u, x+y)+φ(x, y)+φ(u, x+y), u+x+y)L−1α = (c+d+F (u, x+y)+φ(x, y), x+y).

R. H. S.= γTα ∗ δTα = (c + a + φ(x, u), x + u)L−1α ∗ (d + a + φ(y, u), y + u)L−1

α =(a+c+φ(u, x)+φ(x, u)+φ(u, x), x+u)L−1

α ∗(a+d+φ(u, y)+φ(y, u)+φ(u, y), y+u)L−1α =

(a + c + F (u, x) + φ(u, x), x + u)L−1α ∗ (a + d + F (u, y) + φ(u, y), y + u)L−1

α =(c + F (u, x), x) ∗ (d + F (u, y), y)L−1

α = (c + d + F (u, x) + F (u, y) + φ(x, y), x + y).

L(φ) is an Aµ-loop ⇔ L. H. S.=R. H. S. ⇔ F (u, x + y) = F (u, x) + F (u, y).

Corollary 2.1 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. L(φ) is an A-loop if and only if the following identities are true for all codewords u, v, x, y in C.

1. A(u, v, x + y) = A(u, v, x) + A(u, v, y).

2. A(x + y, u, v) = A(x, u, v) + A(y, u, v).

3. F (u, x + y) = F (u, x) + F (u, y).

ProofThe loop L(φ) is an A-loop if and only if it is an Aλ-loop, an Aρ-loop and an Aµ-loop. Thus,by Theorem 2.1, the claim follows.

4

T. Jaiyeola 48

Lemma 2.1 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. If L(φ) is an A-loop, then the following are true in L(φ).

(a) A(u, v, x + y) = A(u, v, x) + A(u, v, y).

(b) A(x + y, u, v) = A(x, u, v) + A(y, u, v).

(c) F (u, x + y) = F (u, x) + F (u, y).

(d) c(u, v, x + y) ≡ [c(u, v, x) + c(u, v, y)] mod 2.

(e) c(x + y, u, v) ≡ [c(x, u, v) + c(y, u, v)] mod 2.

(f) u·x+u·y2

≡ u·(x+y)2

mod 2.

ProofBy (3) and (4), it can be deduced that ; F (u, v) ≡ u·v

2mod 2 and A(u, v, w) ≡ c(u, v, w) mod

2 ∀ u, v, w ∈ C. (a), (b) and (c) follow from Corollary 2.1.

(d)A(u, v, x + y) ≡ c(u, v, x + y) mod 2 (5)

A(u, v, x) ≡ c(u, v, x) mod 2 (6)

A(u, v, y) ≡ c(u, v, y) mod 2 (7)

Adding (5), (6) and (7) and using (a), c(u, v, x + y) ≡ [c(u, v, x) + c(u, v, y)] mod 2.

(e)A(x + y, u, v) ≡ c(x + y, u, v) mod 2 (8)

A(x, u, v) ≡ c(x, u, v) mod 2 (9)

A(y, u, v) ≡ c(y, u, v) mod 2 (10)

Adding (8), (9) and (10) and using (b), c(x + y, u, v) ≡ [c(x, u, v) + c(y, u, v)] mod 2.

(f)

F (u, x + y) ≡ u · (x + y)

2mod 2 (11)

F (u, x) ≡ u · x2

mod 2 (12)

F (u, y) ≡ u · y2

mod 2 (13)

Adding (11), (12) and (13) and using (c), u·x+u·y2

≡ u·(x+y)2

mod 2.

Remark 2.1 As deduced in [14], u · v = ||u||+|v||−||u+v||2

.

5

Code Loops and Some Other Loops 49

3 Homogeneous Loops, Kikkawa Loops, K-Loops,

Cross Inverse Property Loops and Code Loops

Lemma 3.1 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. The following are true.

1. L(φ) is a left homogeneous loop ⇔ A(u, v, x + y) = A(u, v, x) + A(u, v, y).

2. L(φ) is a right homogeneous loop ⇔ A(x + y, u, v) = A(x, u, v) + A(y, u, v).

3. L(φ) is a homogeneous loop ⇔ A(u, v, x + y) = A(u, v, x) + A(u, v, y), A(x + y, u, v) =A(x, u, v) + A(y, u, v) and F (u, x + y) = F (u, x) + F (u, y).

ProofL(φ) is a LIPL and RIPL. The proof of 1. and 2. follow from Theorem 2.1 while 3. followsfrom Corollary 2.1.

Lemma 3.2 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. L(φ) is an AIPL if and only if φ(u + v, u + v) = φ(u, u) + φ(v, v) ∀ u, v ∈ C.

ProofLet x = (a, u), y = (b, v) ∈ L(φ). L(φ) is AIPL if and only if (xy)−1 = x−1y−1 ⇔ (a +b + φ(u, v), u + v)−1 = (a, u)−1 ∗ (b, v)−1 ⇔ (a + b + φ(u, v) + φ(u + v, u + v), u + v) =(a+φ(u, u), u)∗ (b+φ(v, v), v) ⇔ (a+ b+φ(u, v)+φ(u+v, u+v), u+v) = (a+ b+φ(u, u)+φ(v, v) + φ(u, v), u + v) ⇔ φ(u + v, u + v) = φ(u, u) + φ(v, v) ∀ u, v ∈ C.

Lemma 3.3 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. The following are true.

1. L(φ) is a left Kikkawa loop⇔ A(u, v, x+y) = A(u, v, x)+A(u, v, y) and φ(u+v, u+v) =φ(u, u) + φ(v, v).

2. L(φ) is a right Kikkawa loop ⇔ A(x+y, u, v) = A(x, u, v)+A(y, u, v) and φ(u+ v, u+v) = φ(u, u) + φ(v, v).

3. L(φ) is a Kikkawa loop ⇔ A(u, v, x + y) = A(u, v, x) + A(u, v, y), A(x + y, u, v) =A(x, u, v) + A(y, u, v), F (u, x + y) = F (u, x) + F (u, y) and φ(u + v, u + v) = φ(u, u) +φ(v, v).

ProofL(φ) is a IPL The proof follows from Theorem 2.1, Corollary 2.1 and Lemma 3.2.

Lemma 3.4 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. The following are true.

1. L(φ) is a left K-loop ⇔ φ(u + v, u + v) = φ(u, u) + φ(v, v).

6

T. Jaiyeola 50

2. L(φ) is a right K-loop ⇔ φ(u + v, u + v) = φ(u, u) + φ(v, v).

3. L(φ) is a K-loop ⇔ φ(u + v, u + v) = φ(u, u) + φ(v, v).

ProofL(φ) is a Moufang loop. The rest of the proof follow from Lemma 3.2.

Theorem 3.1 Let L(φ) be a code loop on a binary linear code C that is doubly even withfactor set φ. L(φ) is a CIPL if and only φ(u, v) = φ(v, u).

ProofL(φ) is a CIPL if and only if x ·yx−1 = y ∀ x, y ∈ L(φ) ⇔ (a, u)∗ [(b, v)∗ (a, u)−1] = (b, v) ⇔(b+φ(u, u)+φ(v, u)+φ(u, u+ v), v) = (b, v) ⇔ φ(u, v +u) = φ(u, u)+φ(v, u) = φ(u+ v, u).

In L(φ), φ(u, v + u) = φ(u + v, u) ⇔ φ(u, v) = φ(v, u). Thence, the proof is complete.

Remark 3.1 In fact, a code loop is a cross inverse property loop if and only if it is com-mutative : L(φ) is commutative if and only if xy = yx ∀ x, y ∈ L(φ) ⇔ (a, u) ∗ (b, v) =(b, v) ∗ (a, u) ⇔ (a + b + φ(u, v), u + v) = (a + b + φ(v, u), u + v) ⇔ φ(u, v) = φ(v, u).

References

[1] R. H. Bruck (1966), A survey of binary systems, Springer-Verlag, Berlin-Gottingen-Heidelberg, 185pp.

[2] O. Chein, H. O. Pflugfelder and J. D. H. Smith (1990), Quasigroups and Loops : Theoryand Applications, Heldermann Verlag, 568pp.

[3] J. Dene and A. D. Keedwell (1974), Latin squares and their applications, the EnglishUniversity press Lts, 549pp.

[4] A. Drapal (2000), A-loops close to code loops are groups, Comment. Math. Carolinae41,2, 245–249.

[5] O. Chein and E.G. Goodaire (1990), Moufang loops with a unique non-identity commu-tator (associator, square), J. Alg. 130, 369–384.

[6] O. Chein and E.G. Goodaire (1990), Code loops are RA2 loops, J. Alg. 130, 385–387.

[7] E. G. Goodaire, E. Jespers and C. P. Milies (1996), Alternative Loop Rings, NHMS(184),Elsevier, 387pp.

[8] R. L. Jr. Griess (1986), Code loops, J. Alg. 100, 224–234.

[9] M. K. Kinyon, K. Kunen, J.D. Phillips (2001), Every Diassociative A-Loop is Moufang,Proc. Amer. Math. Soc. 130,3, 619–624.

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[10] P. Vojtechovsky, Derived forms and binary linear codes, Mathematics Report NumberM99-10, Deparment of mathematics, Iowa State University.

[11] P. Vojtechovsky (2000), Combinatorial aspects of code loops, Comm. Math. Uni. Car-olinae 41,2, 429–435.

[12] P. Vojtechovsky, Combinatorial polarization, code loops and codes of high level, pro-ceedings of CombinaTexas 2003, published in International Journal of Mathematicsand Mathematical Sciences 29 (2004), 1533–1541

[13] H. O. Pflugfelder (1990), Quasigroups and Loops : Introduction, Sigma series in PureMath. 7, Heldermann Verlag, Berlin, 147pp.

[14] P. Vojtechovsky (2003), Connections between codes, groups and loops, Ph.D thesis,Charles University Czech Republic.

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