This article is cited in
3 papers
On graphs in which neighborhoods of vertices are strongly regular with parameters (85,14,3,2) or (325,54,3,10)
M. M. Isakovaa,
A. A. Makhnevbc,
A. A. Tokbaevaa a Kabardino-Balkar State University, Nal'chik
b Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg
c Ural Federal University named after the First President of Russia B. N. Yeltsin, Ekaterinburg
Abstract:
J. Koolen posed the problem of studying distance regular graphs in which neighborhoods of vertices are strongly regular graphs with nonprincipal eigenvalue at most
$t$ for a given positive integer
$t$. This problem was solved earlier for
$t=3$. In the case
$t=4$, a reduction to graphs in which neighborhoods of vertices have parameters (352,26,0,2), (352,36,0,4), (243,22,1,2), (729,112,1,20), (204,28,2,4), (232,33,2,5), (676,108,2,20), (85,14,3,2), or (325,54,3,10) was obtained. In the present paper, we prove that a distance regular graph in which neighborhoods of vertices are strongly regular with parameters
$(85,14,3,2)$ or
$(325,54,3,10)$ has intersection array
$\{85,70,1;1,14,85\}$ or
$\{325,270,1;1,54,325\}$. In addition, we find possible automorphisms of a graph with intersection array
$\{85,70,1;1,14,85\}$.
Keywords:
strongly regular graph, locally $\mathcal X$-graph, automorphism of a graph.
UDC:
519.17
MSC: 05C25,
20F29 Received: 17.10.2015
DOI:
10.21538/0134-4889-2016-22-3-137-143