English

Generating infinite digraphs by derangements

Combinatorics 2020-08-31 v2

Abstract

A set S\mathcal{S} of derangements (fixed-point-free permutations) of a set VV generates a digraph with vertex set VV and arcs (x,xσ)(x,x^\sigma) for xVx\in V and σS\sigma\in\mathcal{S}. We address the problem of characterising those infinite (simple loopless) digraphs which are generated by finite sets of derangements. The case of finite digraphs was addressed in earlier work by the second and third authors. A criterion is given for derangement generation which resembles the criterion given by De Bruijn and Erd\H{o}s for vertex colourings of graphs in that the property for an infinite digraph is determined by properties of its finite sub-digraphs. The derangement generation property for a digraph is linked with the existence of a finite 11-factor cover for an associated bipartite (undirected) graph.

Keywords

Cite

@article{arxiv.1909.03675,
  title  = {Generating infinite digraphs by derangements},
  author = {Daniel Horsley and Moharram Iradmusa and Cheryl E. Praeger},
  journal= {arXiv preprint arXiv:1909.03675},
  year   = {2020}
}

Comments

14 pages, 4 figures

R2 v1 2026-06-23T11:09:22.886Z