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arXiv · 2510.06417

Hopf bimodules for bialgebroids

Sophie Chemla·Niels Kowalzig
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Abstract

Generalising a result for Hopf algebras, we not only define the four possible types of Hopf modules in the bialgebroid setting but also yield the notion of two-sided two-cosided Hopf modules, also known as Hopf bimodules or tetramodules, in this realm. By explicitly formulating a fundamental theorem for Hopf modules via the concept of Hopf-Galois comodules, we prove that the category of Hopf bimodules can be endowed with the structure of a (pre-)braided monoidal category in two different ways, which, in turn, are shown to be both braided monoidally equivalent to the category of Yetter-Drinfel'd modules, that is, to the monoidal centre of the category of left bialgebroid modules or comodules. As an illustration, we discuss relative Hopf bimodules associated to Ehresmann-Schauenburg bialgebroids.

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BibTeXRIS

Sophie Chemla, Niels Kowalzig. 2025-10-07. Hopf bimodules for bialgebroids. https://arxiv.org/abs/2510.06417

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