Department of

# Mathematics

Seminar Calendar
for events the day of Friday, April 3, 2020.

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events for the
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Questions regarding events or the calendar should be directed to Tori Corkery.
      March 2020             April 2020              May 2020
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1  2  3  4  5  6  7             1  2  3  4                   1  2
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Friday, April 3, 2020

3:00 pm in https://illinois.zoom.us/j/521113604,Friday, April 3, 2020

#### A dynamical obstruction for classification by actions of TSI Polish groups

###### Aristotelis Panagiotopoulos (Caltech Math)

Abstract: A big part of mathematical activity revolves around classification problems. However, not every classification problem has a satisfactory solution, and some classification problems are more complicated than others. Dynamical properties such as generic ergodicity and turbulence are crucial in the development of a rich complexity theory for classification problems. In this talk we will review some of the existing anti-classification techniques and we will introduce a new obstruction for classification by orbit equivalence relations of TSI Polish groups; a topological group is TSI if it admits a compatible two side invariant metric. We will then show that the Wreath product of any two non-compact subgroups of $S_{\infty}$ admits an action whose orbit equivalence relation is generically ergodic with respect to orbit equivalence relations of TSI group actions.
This is joint work with Shaun Allison.

4:00 pm in TBA,Friday, April 3, 2020