Évènement

Thomas Schick
Math. Institut, Göttingen
https://www.uni-math.gwdg.de/schick/index.html

Date(s) : 09/10/2025   iCal
11h00 - 12h00

« Coarse » geometry studies unbounded metric spaces « from far away », ignoring all the fine local structure.
This paradigm is very successfull and underlies e.g. most of geometric group theory.

A « warped cone » is a non-compact metric space built out of the action of a discrete group on a compact manifold.
Its coarse geometry encodes many dynamical properties of the action. It is also an important tool to construct interesting coarse structures.

A powerful tool in coarse geometry are associated operator algebras and their K-theory. These are the home for coarse index invariants, which in turn give restrictions on the geometry.

The coarse Baum-Connes conjecture predicts a way to compute these important K-theory groups by topological methods. First counterexamples to the conjecture have been constructed by Higson and in follow-up work, all based on a single idea.

In joint work with Kitsios and Vigolo, xe produce a new type of counterexample, given by certain warped cones, which works in a very unexpected way.

In the talk, we gently introduce the subject and its main players as described in the abstract, cumulating in how the counterexamples work and how they work unexpectedly.

Emplacement
I2M Saint-Charles - Salle de séminaire

Catégories

• Séminaire