of - indico.math.cnrs.fr · 1 suppose au an are spherescutting mn into a 2n punctured 3 ball andian...
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Models for Out Fu1 X graph Show to HECX E OuttaX2 X handlebody
Show to Homeo X 37 Out tixA DehntwistonDX extends to a homeomorphism
ofX Showthis is in the kernel ofthemapabove3 X puncturedsurface
A homeomorphism ofX preserves the intersection
farm on HLX so the eigenvalues of themap on HelX ane't or come in pairs 1 I
Use this to find an automorphismofFz thatcannot be realized onanysurface
Stallings folds1 If f X Rn is a graphmorphism that
is locally injective provethat f is a homeomorphismDo not assume X is a rose
2 Use Stallings folds to factor the automorphisma Cba b s a E ba ens ca
of Fz Fla b o into a product of peg's and Xxg's
1 Suppose Au An are spherescuttingMn into a 2n punctured 3 ballandIan can the dual basis of it Mnlets be a sphere in Mn UAi separating A andAi
Ef A O0 0An
A O 0 O OAIs
let f be a diffeomorphism exchanging A and Sandfixingall other Ai What is the automorphism
ofqMn has au inducedby f
2 Use Whitehead'salgorithm to decide whethera ab a abb s b a bi and b i b ca bc 1 cab c b a c
ace automorphismsChoose a random set of words and check whetherit's a basis
Lecture comprehension questions1 why does a Dehn twist on a 2 sphere
in Mn S x 5 have order 2 in toHomeoMn2 Describe an inner automorphism in termsoffolding3 Prove the cut vertex lemma