Nuclear Dimension of Twisted $C^*$-Algebras of Virtually Abelian Groups

Abstract

Let $G$ be a finitely generated virtually abelian group and $[σ]\in H^2(G;\mathbb{T})$ such that $σ(x,y)$ is always a root of unity. We show that the nuclear dimension of the twisted group $C^*$-algebra $C^*(G,σ)$ is equal to the rank of a finite index abelian subgroup of $G$. We also show that $\mbox{dim}_{\text{nuc}}(C^*(\mathbb{Z}^r,σ))=r$ if and only if $σ$ is type I.