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SUMMARY:Quasimorphisms on groups of diffeomorphisms - Richard Webb\, Cambr
 idge
DTSTART:20191120T160000Z
DTEND:20191120T170000Z
UID:TALK128224@talks.cam.ac.uk
CONTACT:Ivan Smith
DESCRIPTION:I will explain how to construct an unbounded quasimorphism on 
 the group of isotopically-trivial diffeomorphisms of a surface of genus at
  least two. As a corollary the commutator length and fragmentation norm ar
 e both (stably) unbounded\, which solves an open problem of Burago--Ivanov
 --Polterovich. I will provide some background about these groups before in
 troducing new geometric tools to study them. This is joint work with Jonat
 han Bowden and Sebastian Hensel.
LOCATION:MR13
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