The free wreath product of a discrete group by a quantum automorphism group

Abstract:

Let $\mathbb {G}$ be the quantum automorphism group of a finite dimensional C*-algebra $(B,\psi )$ and $\Gamma$ a discrete group. We want to compute the fusion rules of $\widehat {\Gamma }\wr _* \mathbb {G}$. First of all, we will revise the representation theory of $\mathbb {G}$ and, in particular, we will describe the spaces of intertwiners by using noncrossing partitions. It will allow us to find the fusion rules of the free wreath product in the general case of a state $\psi$. We will also prove the simplicity of the reduced C*-algebra, when $\psi$ is a trace, as well as the Haagerup property of $L^\infty (\widehat {\Gamma }\wr _* \mathbb {G})$, when $\Gamma$ is moreover finite.