Drinfeld-Xu bialgebroid 2-cocycles twist the antipode

Fuente: arXiv
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Main Author: Škoda, Zoran
Format: Preprint
Published: 2026
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author Škoda, Zoran
author_facet Škoda, Zoran
contents 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 $S$ for the original bialgebroid exists, and another expression $V_F$ depending on the 2-cocycle $F$ is invertible, then the expected conjugation formula $S_F(-) = V_F^{-1} S(-) V_F$ indeed produces an invertible antipode $S_F$ for the twisted bialgebroid.
format Preprint
id arxiv_https___arxiv_org_abs_2604_04813
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Drinfeld-Xu bialgebroid 2-cocycles twist the antipode
Škoda, Zoran
Quantum Algebra
Rings and Algebras
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 $S$ for the original bialgebroid exists, and another expression $V_F$ depending on the 2-cocycle $F$ is invertible, then the expected conjugation formula $S_F(-) = V_F^{-1} S(-) V_F$ indeed produces an invertible antipode $S_F$ for the twisted bialgebroid.
title Drinfeld-Xu bialgebroid 2-cocycles twist the antipode
topic Quantum Algebra
Rings and Algebras
url https://arxiv.org/abs/2604.04813