Weak Hopf Algebras, Smash Products and Applications to Adjoint-Stable Algebras

Abstract: For a semisimple quasi-triangular Hopf algebra $\left( H,R\right) $ over a field $k$ of characteristic zero, and a strongly separable quantum commutative $H$-module algebra $A$ over which the Drinfeld element of $H$ acts trivially, we show that $A#H$ is a weak Hopf algebra, and it can be embedded into a weak Hopf algebra $\operatorname{End}A^{\ast}\otimes H$. With these structure, ${A#H}\operatorname{Mod}$ is the monoidal category introduced by Cohen and Westreich, and ${\operatorname{End}A^{\ast}\otimes H}\mathcal{M}$ is tensor equivalent to ${H}\mathcal{M}$. If $A$ is in the M{\"{u}}ger center of ${H}{\mathcal{M}}$, then the embedding is a quasi-triangular weak Hopf algebra morphism. This explains the presence of a subgroup inclusion in the characterization of irreducible Yetter-Drinfeld modules for a finite group algebra.