Martijn Caspers (Münster): The Haagerup property for arbitrary von Neumann algebras

Martijn Caspers (Münster) will give a talk with title: The Haagerup property for arbitrary von Neumann algebras

Abstract: The Haagerup property is an approximation property for both groups and operator algebras that has important applications in for example the Baum-Connes conjecture or von Neumann algebra theory. In this talk we show that the Haagerup property is an intrinsic invariant of an arbitrary von Neumann algebra. We also discuss stability properties of the Haagerup property under constructions as free products, graph products and crossed products. Finally we discuss alternative characterizations in terms of the existence of suitable quadratic forms.