On the Hopf envelope of finite-dimensional bialgebras

Fuente: arXiv
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Auteurs principaux: Ardizzoni, Alessandro, Menini, Claudia, Saracco, Paolo
Format: Preprint
Publié: 2025
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author Ardizzoni, Alessandro
Menini, Claudia
Saracco, Paolo
author_facet Ardizzoni, Alessandro
Menini, Claudia
Saracco, Paolo
contents The Hopf envelope of a bialgebra is the free Hopf algebra generated by the given bialgebra. Its existence, as well as that of the cofree Hopf algebra, is a well-known fact in Hopf algebra theory, but their construction is not particularly handy or friendly. In this note, we offer a novel realisation of the Hopf envelope and of the cofree Hopf algebra of a finite-dimensional bialgebra as a particular quotient and sub-bialgebra, respectively, of the bialgebra itself. Our construction can also be extended to the infinite-dimensional case, provided that the bialgebra satisfies additional conditions, such as being right perfect as an algebra or admitting a $n$-antipode, the latter being a notion hereby introduced. Remarkably, the machinery we develop also allows us to give a new description of the Hopf envelope of a commutative bialgebra and of the cofree cocommutative Hopf algebra of a cocommutative bialgebra.
format Preprint
id arxiv_https___arxiv_org_abs_2504_05821
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Hopf envelope of finite-dimensional bialgebras
Ardizzoni, Alessandro
Menini, Claudia
Saracco, Paolo
Quantum Algebra
Category Theory
Rings and Algebras
Representation Theory
16T05, 16T10, 18M05
The Hopf envelope of a bialgebra is the free Hopf algebra generated by the given bialgebra. Its existence, as well as that of the cofree Hopf algebra, is a well-known fact in Hopf algebra theory, but their construction is not particularly handy or friendly. In this note, we offer a novel realisation of the Hopf envelope and of the cofree Hopf algebra of a finite-dimensional bialgebra as a particular quotient and sub-bialgebra, respectively, of the bialgebra itself. Our construction can also be extended to the infinite-dimensional case, provided that the bialgebra satisfies additional conditions, such as being right perfect as an algebra or admitting a $n$-antipode, the latter being a notion hereby introduced. Remarkably, the machinery we develop also allows us to give a new description of the Hopf envelope of a commutative bialgebra and of the cofree cocommutative Hopf algebra of a cocommutative bialgebra.
title On the Hopf envelope of finite-dimensional bialgebras
topic Quantum Algebra
Category Theory
Rings and Algebras
Representation Theory
16T05, 16T10, 18M05
url https://arxiv.org/abs/2504.05821