Seminar Calendar
for events the day of Thursday, September 8, 2011.

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Questions regarding events or the calendar should be directed to Tori Corkery.
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Thursday, September 8, 2011

BCDE Math/Physics Seminar
12:00 pm   in 464 Loomis Laboratory,  Thursday, September 8, 2011
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Submitted by katz.
 Mike Stone (UIUC Physics)Bott Periodicity and topological insulatorsAbstract: The "periodic table" of topological insulators is related to the two-fold and eightfold Bott periodicity of the groups U(N) and O(2N). I'll try to explain some of these concepts in language accessible to physicists. On the way I hope to explain to mathematicians why down-to-earth Solid State Physicists are suddenly interested in K-Theory.

Number Theory
1:00 pm   in 241 Altgeld Hall,  Thursday, September 8, 2011
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Submitted by berndt.
 Jim Tseng (UIUC)Bad approximation and exceptional sets in homogeneous dynamicsAbstract: There is a well-known correspondence between the approximation of real numbers by rational numbers and a diagonal flow on the space of unimodular lattices. The set of real numbers that are badly approximable is forced to be measure zero by ergodic theory. However, this set is, nevertheless, large: for example, intersect it with a countable number of isometries of itself and the result has Hausdorff dimension one. This conclusion follows immediately from W. Schmidt’s theorem (1966). A suitable generalization of Schmidt’s theorem to systems of affine forms was conjectured in the nineties by D. Kleinbock. I show that a strengthening of the conjecture and various related results hold (joint with M. Einsiedler).

Group Theory Seminar
1:00 pm   in Altgeld Hall 347,  Thursday, September 8, 2011
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Submitted by lukyane2.
 Anton Lukyanenko (UIUC Math)Mappings of Gromov Hyperbolic SpacesAbstract: Gromov hyperbolic spaces and their visual boundaries are a central focus of geometric group theory. I will discuss some standard constructions relating the coarse geometry of a space and analysis on its boundary, in particular relating quasi-isometries to quasi-conformal maps. I will then show that under some natural conditions, a quasi-conformal map of the boundary is induced by a bi-Lipschitz mapping of the space itself.

2:00 pm   in 241 Altgeld Hall,  Thursday, September 8, 2011
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Submitted by lukyane2.
 Stephen Maguire (UIUC Math)A Gentle Introduction to Algebraic Geometry and Invariant Theory.Abstract: I will give an introduction to the field of Algebraic Geometry with examples and towards the end of the talk begin to talk about Algebraic Groups and Invariant Theory. It will mostly be an introductory talk, but will hopefully leave you with a warm feeling towards the wonderful subject of Algebraic Geometry and have whetted your palette with a taste of invariant theory.

Commutative Ring Theory Seminar
3:00 pm   in 243 Altgeld Hall,  Thursday, September 8, 2011
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Submitted by beder.
 Javid Validashti (UIUC Math)Uniform Equivalence of Symbolic and Adic TopologiesAbstract: We show that the symbolic topology defined by a prime ideal is uniformly linearly equivalent to the adic topology for a large class of isolated singularities. This talk is based on a joint work with Craig Huneke and Dan Katz.

Mathematics Colloquium
4:00 pm   in 245 Altgeld Hall,  Thursday, September 8, 2011
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Submitted by kapovich.
 Bruce Hajek (Department of Electrical and Computer Engineering, and Coordinated Science Laboratory, University of Illinois)Peer to Peer Communication in Networks: Issues, Models, and AnalysisAbstract: Distributed protocols for peer to peer file sharing, streaming video, and video on demand have revolutionized the way the majority of information is conveyed over the Internet.  The peers are millions of computers, acting as both clients and servers, downloading and uploading information. Information to be shared is broken into pieces, and the pieces are traded among peers in the network.    This talk will focus on a simple mathematical model and its analysis that illustrate some of the interesting challenges to understanding peer to peer communication, stemming from correlation among the information states of different peers.