English

Triangle-free graphs with diameter 2

Combinatorics 2024-06-04 v1

Abstract

There are finitely many graphs with diameter 22 and girth 5. What if the girth 5 assumption is relaxed? Apart from stars, are there finitely many triangle-free graphs with diameter 22 and no K2,3K_{2,3} subgraph? This question is related to the existence of triangle-free strongly regular graphs, but allowing for a range of co-degrees gives the question a more extremal flavour. More generally, for fixed ss and tt, are there infinitely many twin-free triangle-free Ks,tK_{s,t}-free graphs with diameter 2? This paper presents partial results regarding these questions, including computational results, potential Cayley-graph and probabilistic constructions.

Keywords

Cite

@article{arxiv.2406.00246,
  title  = {Triangle-free graphs with diameter 2},
  author = {Alice Devillers and Nina Kamčev and Brendan McKay and Padraig Ó Catháin and Gordon Royle and Geertrui Van de Voorde and Ian Wanless and David R. Wood},
  journal= {arXiv preprint arXiv:2406.00246},
  year   = {2024}
}
R2 v1 2026-06-28T16:49:16.174Z