TY - JOUR
T1 - Bounding the intersection number c2 of a distance-regular graph with classical parameters (D,b,α,β) in terms of b
AU - Koolen, Jack H.
AU - Lv, Chenhui
AU - Park, Jongyook
AU - Yang, Qianqian
N1 - Publisher Copyright:
© 2024 Elsevier B.V.
PY - 2025/2
Y1 - 2025/2
N2 - 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.
AB - 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.
KW - Classical parameters
KW - Cliques
KW - Distance-regular graphs
KW - Eigenvalues
UR - http://www.scopus.com/inward/record.url?scp=85203558232&partnerID=8YFLogxK
U2 - 10.1016/j.disc.2024.114239
DO - 10.1016/j.disc.2024.114239
M3 - Article
AN - SCOPUS:85203558232
SN - 0012-365X
VL - 348
JO - Discrete Mathematics
JF - Discrete Mathematics
IS - 2
M1 - 114239
ER -