Almost recognizability by spectrum of simple exceptional groups of Lie type

TL;DR

This paper proves that finite groups sharing the spectrum with a simple exceptional Lie-type group are essentially the same, with only finitely many possibilities, except for one specific case.

Contribution

It establishes spectrum-based recognition for all but one exceptional group, showing such groups are uniquely determined up to automorphism within a finite set.

Findings

Finite groups with the same spectrum as $E_7(q)$ are isomorphic to groups between $L$ and its automorphism group.

The result applies to all simple exceptional groups except ${}^3D_4(2)$.

There are finitely many groups with the same spectrum as each such simple group.

Abstract

The spectrum of a finite group is the set of its elements orders. Groups are said to be isospectral if their spectra coincide. For every finite simple exceptional group $L=E_7(q)$, we prove that each finite group isospectral to $L$ is isomorphic to a group $G$ squeezed between $L$ and its automorphism group, that is $L\leq G\leq \operatorname{Aut}L$; in particular, up-to isomorphism, there are only finitely many such groups. This assertion, together with a series of previously obtained results, implies that the same is true for every finite simple exceptional group except the group ${}^3D_4(2)$.