Konrad Wrobel: "Exactness and the topology of the space of invariant random equivalence relations"

Tuesday May 13, 2025, 9:45 AM → 11:45 AM Europe/Paris

Abstract: We characterize exactness of a countable group $\Gamma$ in terms of invariant random equivalence relations (IREs) on $\Gamma$. Specifically, we show that $\Gamma$ is exact if and only if every weak limit of finite IREs is an amenable IRE.  In particular, for exact groups this implies amenability of the restricted rerooting relation associated to the ideal Bernoulli Voronoi tessellation, the discrete analog of the ideal Poisson Voronoi tesselation. This is joint work with H\'ector Jard\'on-S\'anchez, Sam Mellick, and Antoine Poulin.