|
Exceptional pseudogeometric graphs with eigenvalue r
A. Kh. Zhurtov Kabardino-Balkar State University, Nal'chik
Abstract:
A. Neumaier enumerated the parameters of strongly regular graphs with smallest eigenvalue −m. As a corollary it is proved that for a positive integer r there exist only finitely many pseudogeometric graphs for pGs−r(s,t) with parameters different from the parameters of the net pGs−r(s,s−r) and from the parameters of the pGs−r(s,(s−r)(r+1)/r) graph complementary to the line graph of a Steiner 2-design (s is a multiple of r). In this paper we explicitly specify functions f(r) and g(r) such that for s>f(r) or t>g(r) any pseudogeometric graph for pGs−r(s,t) has parameters of the net pGs−r(s,s−r) or parameters of pGs−r(s,(s−r)(r+1)/r).
Keywords:
strongly regular graph, pseudogeometric graph.
Received: 05.06.2018
Citation:
A. Kh. Zhurtov, “Exceptional pseudogeometric graphs with eigenvalue r”, Trudy Inst. Mat. i Mekh. UrO RAN, 24, no. 3, 2018, 68–72
Linking options:
https://www.mathnet.ru/eng/timm1552 https://www.mathnet.ru/eng/timm/v24/i3/p68
|
Statistics & downloads: |
Abstract page: | 118 | Full-text PDF : | 37 | References: | 31 |
|