English

Bireflectionality in the commutator subgroup of a finite orthogonal group

Group Theory 2024-12-13 v2

Abstract

We classify the bireflections (products of 2 involutions) in the commutator subgroup G an orthogonal group O(V) over a finite field GF(q) of characteristic not 2. We show that every element of G is a bireflection if it is reversible (conjugate to its inverse in G), except when q3mod4,dimV2mod4q \equiv 3 \mod 4, \dim V \equiv 2 \mod 4 and VV is hyperbolic. We also classify the reversible elements of G.

Keywords

Cite

@article{arxiv.2411.01323,
  title  = {Bireflectionality in the commutator subgroup of a finite orthogonal group},
  author = {Klaus Nielsen},
  journal= {arXiv preprint arXiv:2411.01323},
  year   = {2024}
}

Comments

11 pages. Corrected an obvious error in remark 3.1. Corrected argument in the proof of lemma 3.10