Title: Trees, buildings, elliptic operators, and K-theory for group C* algebras
Speaker: Professor Paul Baum
Speaker Info: Penn State
Brief Description:
Special Note:

Let G be a locally compact Hausdorff topological group. Examples are Lie groups, discrete groups, p-adic groups, and adelic groups. The (left) regular representation of G gives rise to a C* algebra known as the reduced C* algebra of G. Twenty five years ago P.Baum and A.Connes conjectured an answer to the problem of calculating the K-theory of this C* algebra. When true, the conjecture has corollaries in various branches of mathematics. At the present time, there is no known counter- example and the conjecture has been proved for certain classes of groups. The search for a counter-example has led to some geometrical issues involving expander graphs. This talk will explain the conjecture. The talk is intended for non-specialists. The basic definitions (C* algebra, K-theory etc.) will be carefully stated.

Date: Monday, April 16, 2007
Time: 4:00pm
Where: Lunt 105
Contact Person: Boris Tsygan
Contact email: tsygan@math.northwestern.edu
Contact Phone: 847-467-6446
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