DISTANCE-REGULAR GRAPHS WITH B(T)=1 AND ANTIPODAL DOUBLE-COVERS

Authors
ARAYA M HIRAKI A JURISIC A
Citation
M. Araya et al., DISTANCE-REGULAR GRAPHS WITH B(T)=1 AND ANTIPODAL DOUBLE-COVERS, J COMB TH B, 67(2), 1996, pp. 278-283
Citations number
12
Journal title
JOURNAL OF COMBINATORIAL THEORY SERIES B
ISSN journal
00958956 → ACNP
Volume
67
Issue
2
Year of publication
1996
Pages
278 - 283
Database
ISI
SICI code
0095-8956(1996)67:2<278:DGWBAA>2.0.ZU;2-4
Abstract
Let Gamma be a distance-regular graph of diameter d and valency k > 2. If b(t) = 1 and 2t less than or equal to d, then Gamma is an antipoda l double-cover. Consequently, if f > 2 is the multiplicity of an eigen value of the adjacency matrix of Gamma and if Gamma is not an antipoda l double-cover then d less than or equal to 2f - 3. This result is an improvement of Godsil's bound. (C) 1996 Academic Press, Inc.