Department of

# Mathematics

Seminar Calendar
for events the day of Monday, October 16, 2017.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
    September 2017          October 2017          November 2017
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2    1  2  3  4  5  6  7             1  2  3  4
3  4  5  6  7  8  9    8  9 10 11 12 13 14    5  6  7  8  9 10 11
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24 25 26 27 28 29 30   29 30 31               26 27 28 29 30



Monday, October 16, 2017

3:00 pm in 141 Altgeld Hall,Monday, October 16, 2017

#### Motivating Higher Topos Theory

###### Joseph Rennie   [email] (UIUC)

Abstract: In this talk I will try to argue for the necessity of higher topos theory without using the word “derived” once. I will very briefly discuss the various demonstrations of possibility, but will mostly focus on two aspects which make them interesting: object classifiers, and descent. If time permits, I will give a Weil’ld outline of a connection to physics.

3:00 pm in 243 Altgeld Hall,Monday, October 16, 2017

#### Stability of relative equilibria and isomorphic vector fields

###### Stefan Klajbor (UIUC)

Abstract: Isomorphic vector fields were introduced by Hepworth in his study of vector fields on differentiable stacks. While originating in the realm of stacks, this notion can be useful in the study of equivariant dynamics on manifolds. In particular, we argue in favor of the usefulness of replacing an equivariant vector field by an isomorphic one in order to study the nonlinear stability of relative equilibria. We use this idea to obtain a criterion for nonlinear stability. As an application, we sketch how to use this criterion to obtain Montaldi and Rodrı́guez-Olmos’s criterion for stability of Hamiltonian relative equilibria on symplectic manifolds.

4:00 pm in 245 Altgeld Hall,Monday, October 16, 2017