Mapping Class Groups and Outer Automorphism Groups of Free Groups are C* Simple

Martin R. Bridson and Pierre de la Harpe

Preprint, February 2003. To appear in J. Functional Analysis

We prove that the reduced $C^*$-algebras of centerless mapping class groups and outer automorphism groups of free groups are simple, as are the irreducible pure subgroups of mapping class groups and the analogous subgroups of outer automorphism groups of free groups.