The space of characters, its dynamics, and applications to arithmetic groups.

Group Actions, Geometry and Dynamics
Event time: 
Thursday, September 21, 2023 - 4:00pm
Itamar Vigdorovich
Speaker affiliation: 
Event description: 

To any group G we  associate the space Ch(G) of all characters on G. After defining this space and discussing its interesting properties, I’ll turn to discuss dynamics on such spaces. Our main result is that the action of any​ arithmetic group on the character space of its amenable/solvable radical is stiff, i.e., any probability measure which is stationary under random walks must be invariant. This generalizes a classical theorem of Furstenberg for dynamics on tori. Relying on works of Bader, Boutonnet, Houdayer, and Peterson, this stiffness result is used to deduce dichotomy statements (and ‘charmenability’) for (not necessarily semi-simple) higher rank arithmetic groups pertaining to their normal subgroups, dynamical systems, representation theory and more. The talk is based on a joint work with Uri Bader.