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Geometry-Topology Seminar

Tuesday, December 7, 2021 - 5:15pm

Lei Chen

U Maryland


University of Pennsylvania

via Zoom

The Zoom link will be sent by e-mail to faculty and students at UPenn, and for others can be obtained by e-mailing After the talk, we will stay online for a while for a social visit, with the recording turned off.

In this talk, I discuss the general question of how to obstruct and construct group actions on manifolds. I will focus on large groups like Homeo(M) and Diff(M) about how they can act on another manifold N. The main result is an orbit classification theorem, which fully classifies possible orbits. I will also talk about some low dimensional applications and open questions. This is a joint work with Kathryn Mann.