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JOURNALS // Trudy Instituta Matematiki i Mekhaniki UrO RAN // Archive

Trudy Inst. Mat. i Mekh. UrO RAN, 2016 Volume 22, Number 3, Pages 137–143 (Mi timm1328)

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


 English version:
Proceedings of the Steklov Institute of Mathematics (Supplementary issues), 2017, 299, suppl. 1, 68–74

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