Hilbert modules over $C^*$-categories

Abstract: Hilbert modules over a $C^*$-category were first defined by Mitchener, who also proved that they form a $C^*$-category. An Eilenberg-Watts theorem for Hilbert modules over $C^*$-algebras was proved by Blecher. We follow a similar path to prove an Eilenberg-Watts theorem for Hilbert modules over $C^*$-categories and characterize equivalences of categories of Hilbert modules as being given by tensoring with imprimitivity bimodules. We employ our results to prove several equivalences of bicategories of $C^*$-algebras and $C^*$-categories, and to exhibit a Morita localization of the category of locally small $C^*$-categories.