##### Department of Mathematics,

University of California San Diego

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### Math 211B - Group Actions Seminar

## Forte Shinko

#### UC Berkeley

## Hyperfiniteness of generic actions on Cantor space

##### Abstract:

A countable discrete group is exact if it has a free action on Cantor space which is measure-hyperfinite, that is, for every Borel probability measure on Cantor space, there is a conull set on which the orbit equivalence relation is hyperfinite. For an exact group, it is known that the generic action on Cantor space is measure-hyperfinite, and it is open as to whether the generic action is hyperfinite; an exact group for which the generic action is not hyperfinite would resolve a long-standing open conjecture about whether measure-hyperfiniteness and hyperfiniteness are equivalent. We show that for any countable discrete group with finite asymptotic dimension, its generic action on Cantor space is hyperfinite. This is joint work with Sumun Iyer.

Host: Josh Frisch

### November 2, 2023

### 10:00 AM

APM 7321

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