Bounding the intersection number c2 of a distance-regular graph with classical parameters (D,b,α,β) in terms of b

Jack H. Koolen, Chenhui Lv, Jongyook Park, Qianqian Yang

Research output: Contribution to journalArticlepeer-review

Abstract

Let Γ be a distance-regular graph with classical parameters (D,b,α,β) and b≥1. It is known that Γ is Q-polynomial with respect to θ1, where θ1=[Formula presented]−1 is the second largest eigenvalue of Γ. And it was shown that for a distance-regular graph Γ with classical parameters (D,b,α,β), D≥5 and b≥1, if a1 is large enough compared to b and Γ is thin, then the intersection number c2 of Γ is bounded above by a function of b. In this paper, we obtain a similar result without the assumption that the graph Γ is thin.

Original languageEnglish
Article number114239
JournalDiscrete Mathematics
Volume348
Issue number2
DOIs
StatePublished - Feb 2025

Keywords

  • Classical parameters
  • Cliques
  • Distance-regular graphs
  • Eigenvalues

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