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JOURNALS // Sibirskie Èlektronnye Matematicheskie Izvestiya [Siberian Electronic Mathematical Reports] // Archive

Sib. Èlektron. Mat. Izv., 2017 Volume 14, Pages 1135–1146 (Mi semr853)

This article is cited in 5 papers

Discrete mathematics and mathematical cybernetics

To the theory of Shilla graphs with $b_2=c_2$

A. A. Makhnev, I. N. Belousov

Krasovskii Institute of Mathematics and Mechanics, 16 S.Kovalevskaya Str., 620990, Yekaterinburg, Russia

Abstract: In this paper by using exact formulas for multiplicities of eigenvalues it is founded new infinite serie intersection arrays of $Q$-polynomial Shilla graph with $b_2 = c_2$. Intersection array of $Q$-polynomial Shilla graph $\Gamma$ with $b_2=c_2$ is $\{2rt(2r+1),(2r-1)(2rt+t+1),r(r+t);1,r(r+t),t(4r^2-1)\}$ and for any vertex $u\in \Gamma$ the subgraph $\Gamma_3(u)$ is an antipodal distance-regular graph with the intersection array $\{t(2r+1),(2r-1)(t+1),1;1,t+1,t(2r+1)\}$. In case $t=2r^2-1$ the intersection array is feasible and in case $t=r(2lr-(l+1))$ the intersection array is feasible only if $(l,r)\in \{(1,2),(2,1),(4,1),(6,1)\}$.

Keywords: distance-regular graph, Shilla graph.

UDC: 519.17+512.54

MSC: 05C25

Received October 6, 2017, published November 14, 2017

DOI: 10.17377/semi.2017.14.097



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