# Meeting Details

Title: $\ell^2$-Betti Numbers, Costs of Group Actions, and Random Trees Job Candidate Talk Russell Lyons Abstract: Two important invariants of groups and their measure-preserving actions are $\ell^2$-Betti numbers and cost. Several basic questions about these invariants remain open. We discuss a possible approach to some of these questions that uses random trees. This is joint work with Damien Gaboriau. No background will be assumed.