English

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 SS for the original bialgebroid exists, and another expression VFV_F depending on the 2-cocycle FF is invertible, then the expected conjugation formula SF()=VF1S()VFS_F(-) = V_F^{-1} S(-) V_F indeed produces an invertible antipode SFS_F for the twisted bialgebroid.

Keywords

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