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Groups And Dynamics
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Arie Levit, RLM 11.176: Surface groups and flexibly stable
Wednesday, March 06, 2019, 01:00pm - 02:00pm
A group G is stable in permutations if every almost-action ofG on a finite set is close to some actual action. Part of theinterest in this notion comes from the observation that a non-residuallyfinite stable group cannot be sofic. I will show that surfacegroups are stable in a flexible sense, that is if one is allowedto "add a few extra points" to the permutation. This is the firstnon-trivial stability result for a non-amenable group. The proofis essentially geometric. Along the way, we establish a quantitativevariant of the LERF property for surface groups which may beof independent interest. The talk is based on a joint work withNir Lazarovich and Yair Minsky.
Location: RLM 11.176

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