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SUMMARY:Topological and dynamical obstructions to extending group actions.
  - Sam Nariman (Northwestern University)
DTSTART:20181207T113000Z
DTEND:20181207T123000Z
UID:TALK115474@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:For any 3-manifold $M$ with torus boundary\, we find finitely 
 generated subgroups of $\\Diff_0(\\partial M)$ whose actions do not extend
  to actions on $M$\; in many cases\, there is even no action by homeomorph
 isms.  The obstructions are both dynamical and cohomological in nature.  W
 e also show that\, if $\\partial M = S^2$\, there is no section of the map
  $\\Diff_0(M) \\to \\Diff_0(\\partial M)$.  This answers a question of Ghy
 s for particular manifolds and gives tools for progress on the general pro
 gram of bordism of group actions.  This is a joint work with Kathryn Mann.
LOCATION:Seminar Room 1\, Newton Institute
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