Derangements in permutation groups with two orbits

Fuente: arXiv
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Hauptverfasser: Lee, Melissa, Popiel, Tomasz, Verret, Gabriel
Format: Preprint
Veröffentlicht: 2025
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author Lee, Melissa
Popiel, Tomasz
Verret, Gabriel
author_facet Lee, Melissa
Popiel, Tomasz
Verret, Gabriel
contents A classical theorem of Jordan asserts that if a group $G$ acts transitively on a finite set of size at least $2$, then $G$ contains a derangement (a fixed-point free element). Generalisations of Jordan's theorem have been studied extensively, due in part to their applications in graph theory, number theory and topology. We address a generalisation conjectured recently by Ellis and Harper, which says that if $G$ has exactly two orbits and those orbits have equal length $n \geq 2$, then $G$ contains a derangement. We prove this conjecture in the case where $n$ is a product of two primes, and verify it computationally for $n \leq 30$.
format Preprint
id arxiv_https___arxiv_org_abs_2506_11396
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Derangements in permutation groups with two orbits
Lee, Melissa
Popiel, Tomasz
Verret, Gabriel
Group Theory
A classical theorem of Jordan asserts that if a group $G$ acts transitively on a finite set of size at least $2$, then $G$ contains a derangement (a fixed-point free element). Generalisations of Jordan's theorem have been studied extensively, due in part to their applications in graph theory, number theory and topology. We address a generalisation conjectured recently by Ellis and Harper, which says that if $G$ has exactly two orbits and those orbits have equal length $n \geq 2$, then $G$ contains a derangement. We prove this conjecture in the case where $n$ is a product of two primes, and verify it computationally for $n \leq 30$.
title Derangements in permutation groups with two orbits
topic Group Theory
url https://arxiv.org/abs/2506.11396