Charmenability of arithmetic groups of product type

• DOI: 10.1007/s00222-022-01117-w
• Publication Date: 2022-05-20T23:02:47Z
• Authors: Uri Bader; Rémi Boutonnet; Cyril Houdayer; Jesse Peterson
• Keywords: Equivariant map

39 pages. v3: minor modifications. To appear in Invent. Math<br/>We discuss special properties of the spaces of characters and positive definite functions, as well as their associated dynamics, for arithmetic groups of product type. Axiomatizing these properties, we define the notions of charmenability and charfiniteness and study their applications to the topological dynamics, ergodic theory and unitary representation theory of the given groups. To do that, we study singularity properties of equivariant normal ucp maps between certain von Neumann algebras. We apply our discussion also to groups acting on product of trees.<br/>