English

Strongly regular graphs with parameters (85,14,3,2) do not exist

Combinatorics 2025-04-04 v1

Abstract

We investigate the second smallest unresolved feasible set of parameters of strongly regular graphs, (v,k,λ,μ)=(85,14,3,2)(v,k,\lambda,\mu)=(85,14,3,2). Using the classification of cubic graphs of small degree, we restrict possible local structure of such a graph GG. After that, we exhaustively enumerate possible neighbourhoods of a maximal 33-clique of GG and check them against a variety of conditions, including the combinatorial ones, coming from λ=3\lambda=3 and μ=2\mu=2, as well as the linear algebra ones, utilising the Euclidean representation of GG. These conditions yield contradiction in all cases, and hence, no srg(85,14,3,2)\mathrm{srg}(85,14,3,2) exists.

Keywords

Cite

@article{arxiv.2504.02449,
  title  = {Strongly regular graphs with parameters (85,14,3,2) do not exist},
  author = {Sergey Shpectorov and Tianxiao Zhao},
  journal= {arXiv preprint arXiv:2504.02449},
  year   = {2025}
}
R2 v1 2026-06-28T22:45:04.581Z