On some semidirect products of skew braces arising in Hopf-Galois theory

Fuente: arXiv
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Main Author: Truman, Paul J.
Format: Preprint
Published: 2025
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author Truman, Paul J.
author_facet Truman, Paul J.
contents We classify skew braces that are the semidirect product of an ideal and a left ideal. As a consequence, given a Galois extension of fields $ L/K $ whose Galois group is the semidirect product of a normal subgroup $ A $ and a subgroup $ B $, we classify the Hopf-Galois structures on $ L/K $ that realize $ L^{A} $ via a normal Hopf subalgebra and $ L^{B} $ via a Hopf subalgebra. We show that the Hopf algebra giving such a Hopf-Galois structure is the smash product of these Hopf subalgebras, and use this description to study generalized normal basis generators and questions of integral module structure in extensions of local fields.
format Preprint
id arxiv_https___arxiv_org_abs_2506_04928
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On some semidirect products of skew braces arising in Hopf-Galois theory
Truman, Paul J.
Group Theory
Rings and Algebras
20N99 (Primary), 16T05, 12F10 (Secondary)
We classify skew braces that are the semidirect product of an ideal and a left ideal. As a consequence, given a Galois extension of fields $ L/K $ whose Galois group is the semidirect product of a normal subgroup $ A $ and a subgroup $ B $, we classify the Hopf-Galois structures on $ L/K $ that realize $ L^{A} $ via a normal Hopf subalgebra and $ L^{B} $ via a Hopf subalgebra. We show that the Hopf algebra giving such a Hopf-Galois structure is the smash product of these Hopf subalgebras, and use this description to study generalized normal basis generators and questions of integral module structure in extensions of local fields.
title On some semidirect products of skew braces arising in Hopf-Galois theory
topic Group Theory
Rings and Algebras
20N99 (Primary), 16T05, 12F10 (Secondary)
url https://arxiv.org/abs/2506.04928