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Department of Mathematical Sciences


This week's seminars

Geometry and Topology Seminar: Dynamical and cohomological obstruction to extending group actions

Presented by Sam Nariman, Northwestern

8 November 2018 13:00 in CM301

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 homeomorphisms. The obstructions are both dynamical and cohomological in nature. We 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 Ghys for particular manifolds; and gives tools for progress on the the general program of bordism of group actions. This is joint work with Kathryn Mann.

Contact Mark Powell for more information

Research Seminars by Series

The research groups in the Department of Mathematical Sciences hold several seminar series in term time. Information on date, time and location are available here.

For information on previous years' seminars please see the seminar archives pages.