English

Freeness and divisibility for right $H$-simple left $H$-comodule algebras over a pointed Hopf algebra $H$

Quantum Algebra 2026-07-27 v1

Abstract

Let HH be a pointed Hopf algebra and let AA be a right HH-simple left HH-comodule algebra. We show that every relative (H,A)(H,A)-Hopf module is free as an AA-module and give a characterization of when the category of relative (H,A)(H,A)-Hopf modules is semisimple. We also give an embedding-type structure theorem for AA when HH and AA are N0\mathbb{N}_0-graded. As a consequence, we show that if HH is finite-dimensional and AcoH=kA^{\mathrm{co} H}=\Bbbk, then dimA\dim A divides dimH\dim H.

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Cite

@article{arxiv.2607.24039,
  title  = {Freeness and divisibility for right $H$-simple left $H$-comodule algebras over a pointed Hopf algebra $H$},
  author = {Daisuke Nakamura},
  journal= {arXiv preprint arXiv:2607.24039},
  year   = {2026}
}

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26 pages