Department of

# Mathematics

Seminar Calendar
for events the day of Wednesday, October 23, 2019.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
    September 2019          October 2019          November 2019
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6  7          1  2  3  4  5                   1  2
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Wednesday, October 23, 2019

3:00 pm in 241 Altgeld Hall,Wednesday, October 23, 2019

#### Stormy actions of Bernoulli shifts

###### Joseph Zielinski

Abstract: An equivalence relation is essentially countable when it is Borel reducible to the orbit equivalence relation of some action of a countable group. In a 2005 paper, G. Hjorth introduced the notion of a stormy Polish G-space and showed that this condition is the fundamental obstruction to essential countability for orbit equivalence relations. Specifically, he proved that if a Polish group, G, acts continuously on a Polish space, X, with a Borel orbit equivalence relation then this relation fails to be essentially countable if and only there is a continuous G-equivariant embedding of a stormy action into X. In the first part of this talk we recall the basic concepts and results in Hjorth's work on stormy actions. In the second part, we apply these to the constructions considered in recent joint work with A.S. Kechris, M. Malicki, and A. Panagiotopoulos for actions of non-Archimedian groups and separable Banach spaces.

4:00 pm in 245 Altgeld Hall,Wednesday, October 23, 2019

#### Using Informal Early Feedback (IEF)

###### Lucas Anderson (Center for Innovation in Teaching & Learning )

Abstract: Most teachers get evaluated by their students at the end of the course by implementing ICES. But by then, it is too late to make changes that will make a difference for your current students. You should check in with your students before it is too late. Come to this workshop to learn how to design, implement, and interpret Informal Early Feedback (IEF) to improve the class experience for everyone.

4:00 pm in 447 Altgeld Hall,Wednesday, October 23, 2019

#### Deformations of the Frobenius

###### William Balderrama (Illinois Math)

Abstract: The deformation theory of the Frobenius homomorphism of a group scheme in positive characteristic is rich, and gives rise to various interesting algebraic structures. I'll introduce this problem, talk about the example of the multiplicative group, from which one naturally obtains Witt vectors and the notion of a delta ring, and talk about what is known about the case of elliptic curves.