English

The reduction theorem for relatively maximal subgroups

Group Theory 2021-01-14 v2

Abstract

Let X\mathfrak{X} be a class of finite groups closed under taking subgroups, homomorphic images and extensions. It is known that if AA is a normal subgroup of a finite group GG then the image of an X\mathfrak{X}-maximal subgroup HH of GG in G/AG/A is not, in general, X\mathfrak{X}-maximal in G/AG/A. We say that the reduction X\mathfrak{X}-theorem holds for a finite group AA if, for every finite group GG that is an extension of AA (i. e. contains AA as a normal subgroup), the number of conjugacy classes of X\mathfrak{X}-maximal subgroups in GG and G/AG/A is the same. The reduction X\mathfrak{X}-theorem for AA implies that HA/AHA/A is X\mathfrak{X}-maximal in G/AG/A for every extension GG of AA and every X\mathfrak{X}-maximal subgroup HH of GG. In this paper, we prove that the reduction X\mathfrak{X}-theorem holds for AA if and only if all X\mathfrak{X}-maximal subgroups are conjugate in AA and classify the finite groups with this property in terms of composition factors.

Keywords

Cite

@article{arxiv.1808.10107,
  title  = {The reduction theorem for relatively maximal subgroups},
  author = {Wenbin Guo and Danila O. Revin and Evgeny P. Vdovin},
  journal= {arXiv preprint arXiv:1808.10107},
  year   = {2021}
}

Comments

43 pages

R2 v1 2026-06-23T03:48:43.501Z