The existence of $m$-Haar graphical representations
Abstract
Extending the well-studied concept of graphical regular representations to bipartite graphs, a Haar graphical representation (HGR) of a group is a bipartite graph whose automorphism group is isomorphic to and acts semiregularly with the orbits giving the bipartition. The question of which groups admit an HGR was inspired by a closely related question of Est\'elyi and Pisanski in 2016, as well as Babai's work in 1980 on poset representations, and has been recently solved by Morris and Spiga. In this paper, we introduce the -Haar graphical representation (-HGR) as a natural generalization of HGR to -partite graphs for , and explore the existence of -HGRs for any fixed group. This inquiry represents a more robust version of the existence problem of GSRs as addressed by Du, Feng and Spiga in 2020. Our main result is a complete classification of finite groups without -HGRs.
Cite
@article{arxiv.2409.18716,
title = {The existence of $m$-Haar graphical representations},
author = {Jia-Li Du and Yan-Quan Feng and Binzhou Xia and Da-Wei Yang},
journal= {arXiv preprint arXiv:2409.18716},
year = {2025}
}