Computable presentations of reduced group C*-algebras of hyperbolic groups

Abstract

Answering a question of Thomas Sinclair, we show that the standard presentation of the reduced group C*-algebra $C_r^{\ast }(G)$ of an infinite hyperbolic group $G$ is computable. The main ingredient in proving this result is showing that the Gromov boundary $\partial G$ of $G$ admits a computably compact metric presentation for which the natural action of $G$ on $\partial G$ is computable.

19 pages; first draft; comments welcome!