Structure of an exotic $2$-local subgroup in $E_7(q)$
Group Theory
2026-05-12 v2
Abstract
Let be the finite simple group of Lie type , where is an odd prime power. Then is an index subgroup of the adjoint group , which is also denoted by and known as the group of inner-diagonal automorphisms. It was proven by Cohen--Liebeck--Saxl--Seitz (1992) that there is an elementary abelian -subgroup of order in , such that , and . Furthermore, such an is unique up to conjugacy in . It is known that is always a maximal subgroup of , and is a maximal subgroup of unless . In this note, we describe the structure of . It turns out that if and only if .
Cite
@article{arxiv.2409.20281,
title = {Structure of an exotic $2$-local subgroup in $E_7(q)$},
author = {Mikko Korhonen},
journal= {arXiv preprint arXiv:2409.20281},
year = {2026}
}
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9 pages