English

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

Number Theory 2024-11-05 v2 Group Theory Rings and Algebras

Abstract

Let L/KL/K be any finite Galois extension with Galois group GG. It is known by Chase and Sweedler that the Hopf--Galois correspondence is injective for every Hopf--Galois structure on L/KL/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/KL/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 GG for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure on any GG-Galois extension. In this paper, using a similar approach, we shall classify the groups NN for which the Hopf--Galois correspondence is bijective for every Hopf--Galois structure of type NN on any Galois extension.

Keywords

Cite

@article{arxiv.2406.15800,
  title  = {Classification of the types for which every Hopf--Galois correspondence is bijective},
  author = {Lorenzo Stefanello and Cindy Tsang},
  journal= {arXiv preprint arXiv:2406.15800},
  year   = {2024}
}

Comments

10 pages; modified the definitions of H in Examples 3.1 to 3.5 based on referee's suggestions