English

Generalized (co)integrals on coideal subalgebras

Quantum Algebra 2018-10-31 v2 Rings and Algebras

Abstract

Given a a Hopf algebra HH, its left coideal subalgebra AA and a non-zero multiplicative functional μ\mu on AA, we define the space of left μ\mu-integrals LμAAL^A_\mu\subset A. We observe that dimLμA=1\dim L^A_\mu=1 if AA is a Frobenius algebra and we conclude this equality for finite dimensional left coideal subalgebras of a weakly finite Hopf algebra. In general we prove that if dimLμA>0\dim L^A_\mu>0 then dimA<\dim A <\infty. Given a group-like element gHg\in H we define the space LAgAL^g_{ A}\subset A' of gg-cointegrals on A A and linking this concept with the theory of μ\mu-integrals we observe that: - every semisimple left coideal subalgebra AHA\subset H which is preserved by the antipode squared admits a faithful 11-cointegral; - every unimodular finite dimensional left coideal subalgebra AHA\subset H admitting a faithful 11-cointegral is preserved by the antipode square; - every non-degenerate right group-like projection in a cosemisimple Hopf algebra is a two sided group-like projection. Finally we list all ε\varepsilon-integrals for left coideals subalgebras in Taft algebras and we list all gg-cointegrals on them.

Keywords

Cite

@article{arxiv.1810.07114,
  title  = {Generalized (co)integrals on coideal subalgebras},
  author = {Paweł Kasprzak},
  journal= {arXiv preprint arXiv:1810.07114},
  year   = {2018}
}

Comments

The results are essentially the same but the presentation of them and their proofs was improved. In Section 5 the list of $\varepsilon$-integrals was completed with the case missing in the previous version

R2 v1 2026-06-23T04:42:02.347Z