Research output: Contribution to journal › Article › peer-review
Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - On Graphs in Which the Neighborhoods of Vertices Are Edge-Regular Graphs without 3-Claws
AU - Chen, M.
AU - Makhnev, A.
AU - Nirova, M.
N1 - This research was supported by the National Natural Science Foundation of China (project no. 12171126) and by a grant from the Engineering Modeling and Statistical Computing Laboratory of the Hainan Province.
PY - 2023/12/1
Y1 - 2023/12/1
N2 - The triangle-free Krein graph Kre(r) is strongly regular with parameters (Formula presented.). The existence of such graphs is known only for r = 1 (the complement of the Clebsch graph) and r = 2 (the Higman–Sims graph). A.L. Gavrilyuk and A.A. Makhnev proved that the graph Kre3 does not exist. Later Makhnev proved that the graph Kre4 does not exist. The graph Kre(r) is the only strongly regular triangle-free graph in which the antineighborhood of a vertex (Formula presented.) is strongly regular. The graph (Formula presented.) has parameters (Formula presented.). This work clarifies Makhnev’s result on graphs in which the neighborhoods of vertices are strongly regular graphs without 3-cocliques. As a consequence, it is proved that the graph Kre(r) exists if and only if the graph (Formula presented.) exists and is the complement of the block graph of a quasi-symmetric 2-design.
AB - The triangle-free Krein graph Kre(r) is strongly regular with parameters (Formula presented.). The existence of such graphs is known only for r = 1 (the complement of the Clebsch graph) and r = 2 (the Higman–Sims graph). A.L. Gavrilyuk and A.A. Makhnev proved that the graph Kre3 does not exist. Later Makhnev proved that the graph Kre4 does not exist. The graph Kre(r) is the only strongly regular triangle-free graph in which the antineighborhood of a vertex (Formula presented.) is strongly regular. The graph (Formula presented.) has parameters (Formula presented.). This work clarifies Makhnev’s result on graphs in which the neighborhoods of vertices are strongly regular graphs without 3-cocliques. As a consequence, it is proved that the graph Kre(r) exists if and only if the graph (Formula presented.) exists and is the complement of the block graph of a quasi-symmetric 2-design.
UR - http://www.scopus.com/inward/record.url?partnerID=8YFLogxK&scp=85185146255
UR - https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=tsmetrics&SrcApp=tsm_test&DestApp=WOS_CPL&DestLinkType=FullRecord&KeyUT=001163182700004
U2 - 10.1134/S0081543823060044
DO - 10.1134/S0081543823060044
M3 - Article
VL - 323
SP - S53-S55
JO - Proceedings of the Steklov Institute of Mathematics
JF - Proceedings of the Steklov Institute of Mathematics
SN - 0081-5438
IS - S1
ER -
ID: 53754191