The Selfless Dichotomy

Abstract

The purpose of this note is to address the gap in the stable rank one/purely infinite dichotomy of selfless $C^{\ast }$-probability spaces. In particular, we show that nonfaithful selfless $C^{\ast }$-probability spaces are purely infinite, simple. This completes the dichotomy: Every selfless $C^{\ast }$-algebra either has stable rank one or is purely infinite. Notably, this shows that every selfless $C^{\ast }$-algebra is pure. To accomplish this, we show that infinite reduced free products of $C^{\ast }$-probability spaces with nonfaithful states inducing faithful GNS representations are often purely infinite, simple. Having resolved the dichotomy, we improve existing permanence properties of selfless $C^{\ast }$-probability spaces, make progress on a conjecture of Choda and Dykema, and produce several new isomorphisms arising from reduced free products.

8 pages, minor changes made ahead of submission, comments welcome