Drinfeld-Xu bialgebroid 2-cocycles twist the antipode
Quantum Algebra
2026-04-07 v1 Rings and Algebras
Abstract
Ping Xu generalized Drinfeld 2-cocycles from bialgebras to associative bialgebroids over noncommutative base algebras. Any counital Drinfeld--Xu 2-cocycle twists the base algebra of the bialgebroid and a comultiplication on the total algebra, obtaining a new, twisted bialgebroid. Antipodes for bialgebroids have been considered, but finding a general way to twist the antipode, which is straightforward in the Hopf algebra case, appeared somewhat elusive. In this article, we prove that if an invertible antipode for the original bialgebroid exists, and another expression depending on the 2-cocycle is invertible, then the expected conjugation formula indeed produces an invertible antipode for the twisted bialgebroid.
Cite
@article{arxiv.2604.04813,
title = {Drinfeld-Xu bialgebroid 2-cocycles twist the antipode},
author = {Zoran Škoda},
journal= {arXiv preprint arXiv:2604.04813},
year = {2026}
}
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16 pages