Examples of diameter-2 graphs with no triangle or $K_{2,t}$
Combinatorics
2026-02-17 v1
Abstract
For each let denote the class of graphs other than stars that have diameter and contain neither a triangle nor a . The famous Hoffman--Singleton Theorem implies that is finite. Recently Wood suggested the study of for and conjectured that is finite for all . In this note we show that (1) is infinite, (2) contains infinitely many regular graphs, and (3) contains infinitely many Cayley graphs. Our and examples are based on so-called crooked graphs, first constructed by de Caen, Mathon, and Moorhouse. Our examples are Cayley graphs with vertex set for prime .
Keywords
Cite
@article{arxiv.2508.19646,
title = {Examples of diameter-2 graphs with no triangle or $K_{2,t}$},
author = {Sean Eberhard and Vladislav Taranchuk and Craig Timmons},
journal= {arXiv preprint arXiv:2508.19646},
year = {2026}
}
Comments
8 pages