$C^{\ast }$-index of observable algebra in the field algebra determined by a normal group

Xin Qiaoling, Jiang Lining

Let $G$ be a finite group and $H$ a normal subgroup. $D(H;G)$ is the crossed product of $C(H)$ and $\mathbb{C}G$ which is only a subalgebra of $D(G)$, the quantum double of $G$. One…