English

There does not exist a distance-regular graph with intersection array $\{80, 54,12; 1, 6, 60\}$

Combinatorics 2018-09-27 v1

Abstract

In this paper we will show that there does not exist a distance-regular graph Γ\Gamma with intersection array {80,54,12;1,6,60}\{80, 54,12; 1, 6, 60\}. We first show that a local graph Δ\Delta of Γ\Gamma does not contain a coclique with 5 vertices, and then we prove that the graph Γ\Gamma is geometric by showing that Δ\Delta consists of 4 disjoint cliques with 20 vertices. Then we apply a result of Koolen and Bang to the graph Γ\Gamma, and we could obtain that there is no such a distance-regular graph.

Cite

@article{arxiv.1809.10029,
  title  = {There does not exist a distance-regular graph with intersection array $\{80, 54,12; 1, 6, 60\}$},
  author = {Jack H. Koolen and Quaid Iqbal and Jongyook Park and Masood Ur Rehman},
  journal= {arXiv preprint arXiv:1809.10029},
  year   = {2018}
}

Comments

15 pages

R2 v1 2026-06-23T04:19:09.101Z