English

Hopf--Galois structures of cyclic type on parallel extensions of prime power degree

Group Theory 2026-05-08 v2 Number Theory Rings and Algebras

Abstract

Let L/KL/K be any finite separable extension with normal closure L~/K\widetilde{L}/K. An extension L/KL'/K is said to be \textit{parallel to L/K} if LL' is an intermediate field of L~/K\widetilde{L}/K with [L:K]=[L:K][L':K]=[L:K]. We study the following question -- Given that L/KL/K admits a Hopf--Galois structure of type NN, does it imply that every extension parallel to L/KL/K also admits a Hopf--Galois structure of type NN? We completely solve this problem when the degree [L:K][L:K] is a prime power and the type NN is cyclic. Our approach is group-theoretic and uses the work of Greither--Pareigis and Byott.

Keywords

Cite

@article{arxiv.2510.14473,
  title  = {Hopf--Galois structures of cyclic type on parallel extensions of prime power degree},
  author = {Andrew Darlington and Cindy Tsang},
  journal= {arXiv preprint arXiv:2510.14473},
  year   = {2026}
}

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32 pages