题 目：Cleft Extensions and Quotients of Twisted Doubles
报 告 人：Prof Siu-Hung Ng
Louisiana State University, USA
The construction of twisted quantum doubles $D^\omega(G)$ of finite groups $G$ was motivated by holomorphic orbifold in conformal field theory. In particular, their representation categories are modular. On the other hand, $D^\omega(G)$ can also be viewed as a cleft extension of certain quasi-Hopf algebras in the sense of Masuoka. In this talk, we will discuss a generalized construction of braided quasi-Hopf algebras $D^\omega(G,A)$ from a central subgroup $A$ of a finite group G as a
quotient of the cleft extension of some twisted quantum double of $G$. The modularity of $D^\omega(G,A)$ is determined by the non-degeneracy of the associated bicharacter defined on $A$.