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Automorphisms of an $AT4(4,4,2)$-graph and of the corresponding strongly regular graphs
K. S. Efimovabc a Ural Federal University, Ekaterinburg, 620002 Russia
b Ural State University of Economics, Ekaterinburg, 620144 Russia
c Krasovskii Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, 620990 Russia
Abstract:
A.A. Makhnev, D.V. Paduchikh, and M. M. Khamgokova gave a classification of distance-regular locally\linebreak
$GQ(5,3)$-graphs. In particular, there arises an
$AT4(4,4,2)$-graph with intersection array
$\{96,75,16,1;1,16,75,96\}$ on
$644$ vertices. The same authors proved that an
$AT4(4,4,2)$-graph is not a locally
$GQ(5,3)$-graph. However, the existence of an
$AT4(4,4,2)$-graph that is a locally pseudo
$GQ(5,3)$-graph is unknown. The antipodal quotient of an
$AT4(4,4,2)$-graph is a strongly regular graph with parameters
$(322,96,20,32)$. These two graphs are locally pseudo
$GQ(5,3)$-graphs. We find their possible automorphisms. It turns out that the automorphism group of a distance-regular graph with intersection array
$\{96,75,16,1;1,16,75,96\}$ acts intransitively on the set of its antipodal classes.
Keywords:
distance-regular graph, graph automorphism.
UDC:
519.17
MSC: 05B25 Received: 01.09.2017
DOI:
10.21538/0134-4889-2017-23-4-119-127