Friday 11 March 2022, 16:00 – 17:00, M108

In this talk I will start with an elementary introduction of group actions on the Hyperfinite II_1 factor and their classification results by Connes, Jones and Ocneanu. I will then discuss more generalised notions of actions (in particular anomalous actions), how they fit into the framework of “symmetries”, and their study on the Hyperfinite II_1 factor. I will then turn to C*-algebras and discuss some existence and uniqueness results of these anomalous actions in that setting, this turns out to be more subtle than in the case of von Neumann algebras as K-theoretic invariants come into play. The results I will discuss in the C*-setting are joined work with Samuel Evington.

Sergio Giron Pacheco (University of Oxford, England)