Geodesic
On strongly regular graphs with eigenvalue $\mu$ and their extensions
Trudy Instituta matematiki i mehaniki, Trudy Instituta Matematiki i Mekhaniki UrO RAN, Tome 19 (2013) no. 3, pp. 207-214 Cet article a éte moissonné depuis la source Math-Net.Ru

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Let $\mathcal M$ be a class of strongly regular graphs for which $\mu$ is a non-principal eigenvalue. Note that the neighborhood of any vertex of an $AT4$ graph lies in $\mathcal M$. We describe parameters of graphs from $\mathcal M$ and find intersection arrays of $AT4$ graphs in which neighborhoods of vertices lie in chosen subclasses from $\mathcal M$. In particular, an $AT4$ graph in which the neighborhoods of vertices do not contain triangles is the Conway–Smith graph with parameters $(p,q,r)=(1,2,3)$ or the first Soicher graph with parameters $(p,q,r)=(2,4,3)$.
Keywords: strongly regular graph, $AT4$-graph, locally $\mathcal M$-graph. 
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A. A. Makhnev; D. V. Paduchikh. On strongly regular graphs with eigenvalue $\mu$ and their extensions. Trudy Instituta matematiki i mehaniki, Trudy Instituta Matematiki i Mekhaniki UrO RAN, Tome 19 (2013) no. 3, pp. 207-214. http://geodesic.mathdoc.fr/item/TIMM_2013_19_3_a20/

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