Operator Theory Seminar

Ionut Chifan
"Symmetry groups of $C^*$-algebras"

Using a combination of powerful techniques from von Neumann algebras and $C^*$-algebras I will introduce a new class of non-amenable countable discrete groups $G$ which can be entirely reconstructed from their reduced $C^*$-algebras (ie, $C^*$-superrigid groups).  Specifically, our groups appear as generalized wreath products with non-amenable core. Currently, there is available only one family of non-amenable $C^*$-superrigid groups (from the realm of amalgams) and our results add numerous novel examples in this direction. As a byproduct we are also able to completely describe the automorphism group $\operatorname{Aut}(C^{*}_{r}(G))$ in the same spirit with Houghton and Segal’s results in group theory from the 60’s and 70’s. This is based on a joint work with Alec Diaz-Arias.

Event Date: 
September 10, 2019 - 1:30pm to 2:30pm
309 VAN
Calendar Category: 
Seminar Category: 
Operator Theory