| Résume | In this talk we provide a class of infinite measure preserving actions that are W*-superrigid, i.e. the action can be completely recovered from its crossed product von Neumann algebra. In particular, we show that if $S$ is a set of primes that contains at least two elements, then the action of $PSL_2(\mathbb Z[S^{-1}])$ by fractional transformations on the upper half plane is W*-superrigid. This is a joint work with Stefaan Vaes. |
