On set-theoretic solutions of pentagon equation and positive basis Hopf algebras

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Hauptverfasser: Colazzo, Ilaria, Janssens, Geoffrey
Format: Preprint
Veröffentlicht: 2026
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author Colazzo, Ilaria
Janssens, Geoffrey
author_facet Colazzo, Ilaria
Janssens, Geoffrey
contents We investigate the connection between bijective, not necessarily finite, set-theoretic solutions of the pentagon equation and Hopf algebras. Firstly, we prove that finite solutions correspond to Hopf algebras with the positive basis property. As a corollary we generalise Lu-Yan-Zhu classification to arbitrary characteristic $0$ fields $k$. Secondly, we study the general problem of when a Hopf algebra has a basis yielding a set-theoretic solution. Finally, we classify all (co)commutative bijective solutions. This result requires to obtain a description of all bases of a group algebra $k[G]$ yielding a set-theoretic solution. We namely show that such bases correspond, through a Fourier transform, to splittings $A \rtimes N$ of $G$ with $A$ a finite abelian group.
format Preprint
id arxiv_https___arxiv_org_abs_2601_22089
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On set-theoretic solutions of pentagon equation and positive basis Hopf algebras
Colazzo, Ilaria
Janssens, Geoffrey
Rings and Algebras
Quantum Algebra
We investigate the connection between bijective, not necessarily finite, set-theoretic solutions of the pentagon equation and Hopf algebras. Firstly, we prove that finite solutions correspond to Hopf algebras with the positive basis property. As a corollary we generalise Lu-Yan-Zhu classification to arbitrary characteristic $0$ fields $k$. Secondly, we study the general problem of when a Hopf algebra has a basis yielding a set-theoretic solution. Finally, we classify all (co)commutative bijective solutions. This result requires to obtain a description of all bases of a group algebra $k[G]$ yielding a set-theoretic solution. We namely show that such bases correspond, through a Fourier transform, to splittings $A \rtimes N$ of $G$ with $A$ a finite abelian group.
title On set-theoretic solutions of pentagon equation and positive basis Hopf algebras
topic Rings and Algebras
Quantum Algebra
url https://arxiv.org/abs/2601.22089