Actions of measured quantum groupoids on a finite basis

Abstract

In this article, we generalize to the case of measured quantum groupoids on a finite basis some important results concerning actions of locally compact quantum groups on C*-algebras [S. Baaj, G. Skandalis and S. Vaes, 2003]. Let $\cal G$ be a measured quantum groupoid on a finite basis. We prove that if $\cal G$ is regular, then any weakly continuous action of $\cal G$ on a C*-algebra is necessarily strongly continuous. Following [S. Baaj and G. Skandalis, 1989], we introduce and investigate a notion of $\cal G$-equivariant Hilbert C$^*$-modules. By applying the previous results and a version of the Takesaki-Takai duality theorem obtained in [S. Baaj and J. C., 2015] for actions of $\cal G$, we obtain a canonical equivariant Morita equivalence between a given $\cal G$-C$^*$-algebra $A$ and the double crossed product $(A\rtimes{\cal G})\rtimes\widehat{\cal G}$.