Members Seminar

cdh methods in K-theory and Hochschild homology

Charles Weibel
Rutgers University; Member, School of Mathematics
November 11, 2013

This is intended to be a survey talk, accessible to a general mathematical audience. The cdh topology was created by Voevodsky to extend motivic cohomology from smooth varieties to singular varieties, assuming resolution of singularities (for example complex varieties). The slogan is that every variety is locally smooth in this topology. Adapting this to algebraic K-theory has led to several breakthroughs in computation, and clarified connections between the "singular" part of K-theory and Hodge theory.

Conformal Dynamics in Pseudo-Riemannian Geometry: Around a Question of A. Lichnerowicz

Charles Frances
Universite Paris-Sud 11; Member, School of Mathematics
April 1, 2013

In the middle of the sixties, A. Lichnerowicz raised the following simple question: “Is the round sphere the only compact Riemannian manifold admitting a noncompact group of conformal transformations?” The talk will present the developments which arose from Lichnerowicz's question. It will be an opportunity to see diverse aspects of conformal dynamics in Riemannian, as well as Lorentzian geometry