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Sibirskie Èlektronnye Matematicheskie Izvestiya [Siberian Electronic Mathematical Reports], 2023, Volume 20, Issue 1, Pages 207–210
DOI: https://doi.org/10.33048/semi.2023.20.017
(Mi semr1581)
 

Mathematical logic, algebra and number theory

Distance-regular graph with intersection array $\{143,108,27;1,12,117\}$ does not exist

A. A. Makhneva, M. M. Isakovab, A. A. Tokbaevab

a N.N. Krasovskii Institute of Mathematics and Mechanics of the Ural Branch of the Russian Academy of Sciences, str. S.Kovalevskaya, 16, 620990, Yekaterinburg, Russia
b Kabardino-Balkarian State University named after H.M. Berbekov, str. Chernyshevsky, 175, 360004, Nalchik, Russia
References:
Abstract: There is a formally self-dual distance-regular graph $\Gamma$ with classical parameters $d=3$, $b=\alpha+1=q$, $\beta=q^2+q-1$ and intersection array $\{(q^2+q-1)(q^2+q+1),(q^2+q)q^2,q^3;1,(q^2+q),q^2(q^2+q+1)\}$. For the graph $\Gamma$ we have the strongly regular graphs $\Gamma_2$ and $\Gamma_3$ ($\Gamma_3$ is pseuqo-geometric for $pG_{q-1}(q^2+q-1,(q^2+q+1)(q-1))$).
It is proved that a distance-regular graph with intersection array $\{143,108,27;1,12,117\}$ ($q=3$) does not exist.
Keywords: distance-regular graph, formally self-dual graph, triple intersection numbers.
Funding agency Grant number
Russian Foundation for Basic Research 20-51-53013
Received October 16, 2021, published March 9, 2023
Document Type: Article
UDC: 519.17
MSC: 05C25
Language: Russian
Citation: A. A. Makhnev, M. M. Isakova, A. A. Tokbaeva, “Distance-regular graph with intersection array $\{143,108,27;1,12,117\}$ does not exist”, Sib. Èlektron. Mat. Izv., 20:1 (2023), 207–210
Citation in format AMSBIB
\Bibitem{MakIsaTok23}
\by A.~A.~Makhnev, M.~M.~Isakova, A.~A.~Tokbaeva
\paper Distance-regular graph with intersection array $\{143,108,27;1,12,117\}$ does not exist
\jour Sib. \`Elektron. Mat. Izv.
\yr 2023
\vol 20
\issue 1
\pages 207--210
\mathnet{http://mi.mathnet.ru/semr1581}
\crossref{https://doi.org/10.33048/semi.2023.20.017}
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