Department of

# Mathematics

Seminar Calendar
for events the day of Monday, December 2, 2013.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
    November 2013          December 2013           January 2014
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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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Monday, December 2, 2013

10:00 am in Altgeld Hall,Monday, December 2, 2013

#### Relative equilibria and vector fields on stacks

###### Eugene Lerman (UIUC Math)

Abstract: TBA

4:00 pm in 241 Altgeld Hall,Monday, December 2, 2013

#### Thin groups: arithmetic and beyond

###### Elena Fuchs (California-Berkeley)

Abstract: In 1643, Rene Descartes discovered a formula relating curvatures of circles in Apollonian circle packings, constructed by Apollonius of Perga in 200 BC. This formula has recently led to a connection between the construction of Apollonius and orbits of a certain so-called thin subgroup G of GL_4(Z). This connection is key in recent results on the arithmetic of Apollonian packings, which I will describe in this talk. A crucial ingredient in the proofs is the spectral gap coming from families of expander graphs associated to G -- this gap is far less understood in the case of thin groups than that of non-thin groups. Motivated by this problem, I will then discuss the ubiquity of thin groups and present results on thinness of monodromy groups of hypergeometric equations in the case where these groups act on hyperbolic space.

4:00 pm in 141 Altgeld Hall,Monday, December 2, 2013

#### Strategies for a Successful Job Search

###### Katherine Chun Eriksen (Graduate College Career Services)

Abstract: Presentation and discussion on how to identify and apply for nonacademic internships or full-time positions. All mathematics graduate students are welcome.

5:00 pm in 241 Altgeld,Monday, December 2, 2013