Classification of the types for which every Hopf--Galois correspondence is bijective

Fuente: arXiv
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Auteurs principaux: Stefanello, Lorenzo, Tsang, Cindy
Format: Preprint
Publié: 2024
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author Stefanello, Lorenzo
Tsang, Cindy
author_facet Stefanello, Lorenzo
Tsang, Cindy
contents Let $L/K$ be any finite Galois extension with Galois group $G$. It is known by Chase and Sweedler that the Hopf--Galois correspondence is injective for every Hopf--Galois structure on $L/K$, but it need not be bijective in general. Hopf--Galois structures are known to be related to skew braces, and recently, the first-named author and Trappeniers proposed a new version of this connection with the property that the intermediate fields of $L/K$ in the image of the Hopf--Galois correspondence are in bijection with the left ideals of the associated skew brace. As an application, they classified the groups $G$ for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure on any $G$-Galois extension. In this paper, using a similar approach, we shall classify the groups $N$ for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure of type $N$ on any Galois extension.
format Preprint
id arxiv_https___arxiv_org_abs_2406_15800
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Classification of the types for which every Hopf--Galois correspondence is bijective
Stefanello, Lorenzo
Tsang, Cindy
Number Theory
Group Theory
Rings and Algebras
12F10, 16T05, 20N99
Let $L/K$ be any finite Galois extension with Galois group $G$. It is known by Chase and Sweedler that the Hopf--Galois correspondence is injective for every Hopf--Galois structure on $L/K$, but it need not be bijective in general. Hopf--Galois structures are known to be related to skew braces, and recently, the first-named author and Trappeniers proposed a new version of this connection with the property that the intermediate fields of $L/K$ in the image of the Hopf--Galois correspondence are in bijection with the left ideals of the associated skew brace. As an application, they classified the groups $G$ for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure on any $G$-Galois extension. In this paper, using a similar approach, we shall classify the groups $N$ for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure of type $N$ on any Galois extension.
title Classification of the types for which every Hopf--Galois correspondence is bijective
topic Number Theory
Group Theory
Rings and Algebras
12F10, 16T05, 20N99
url https://arxiv.org/abs/2406.15800