Conferences - Seminars

  13:00-14:00 MA A3 30

Every action of a group on a rooted tree induces an action on the boundary of the tree. This action yields various representations of the group on spaces of functions on the boundary. In this talk we discuss the structure of such representations. After reviewing of the basic concepts, we will introduce locally 2-transitive actions ... Read more about "Groups acting on rooted trees and representations on the boundary"
By Steffen Kionke (KIT)
  10:15-11:30 CM 1 113

It is a classical problem to recover a discrete group from various rings or algebras associated with it, such as the integral group ring (cf. the Whitehead group and the Whitehead torsion). By analogy, in an operator algebraic framework we want to recover torsion-free groups from certain topological completions of the complex group ring, such ... Read more about "Topology Seminar: C*-superrigidiity of nilpotent groups"
By Sven Raum (EPFL)
  10:15-11:15 CM 1 113

Stratified spaces appear as natural objects in singularity theory. Goresky and MacPherson introduced intersection cohomology to extend cohomological properties of closed manifolds to stratified spaces, and it proved to be a powerful tool to study those objects. However, intersection cohomology is not homotopy invariant, rather it is invariant with respect to homotopies that "preserve" the ... Read more about "Topology Seminar: Stratified homotopy theory"
By Sylvain Douteau (Université de Picardie)