scholarly journals Binary Representations of Regular Graphs

2011 ◽  
Vol 2011 ◽  
pp. 1-15
Author(s):  
Yury J. Ionin
Keyword(s):  
Regular Graph ◽  
Line Graph ◽  
Strongly Regular Graph ◽  
Regular Graphs ◽  
Spherical Representation ◽  
Least Eigenvalue ◽  
Vertex Set ◽  
Strongly Regular ◽  
Distance Set ◽  
Hamming Space

For any 2-distance set in the n-dimensional binary Hamming space , let be the graph with as the vertex set and with two vertices adjacent if and only if the distance between them is the smaller of the two nonzero distances in . The binary spherical representation number of a graph , or bsr(), is the least n such that is isomorphic to , where is a 2-distance set lying on a sphere in . It is shown that if is a connected regular graph, then bsr, where b is the order of and m is the multiplicity of the least eigenvalue of , and the case of equality is characterized. In particular, if is a connected strongly regular graph, then bsr if and only if is the block graph of a quasisymmetric 2-design. It is also shown that if a connected regular graph is cospectral with a line graph and has the same binary spherical representation number as this line graph, then it is a line graph.

scholarly journals On strongly regular graphs with m2 = qm3 and m3 = qm2 where q ∈ Q

2021 ◽  
Vol 109 (123) ◽  
pp. 35-60
Author(s):  
Mirko Lepovic
Keyword(s):  
Regular Graph ◽  
Complete Graph ◽  
Strongly Regular Graph ◽  
Strongly Regular Graphs ◽  
Regular Graphs ◽  
Strongly Regular

We say that a regular graph G of order n and degree r ? 1 (which is not the complete graph) is strongly regular if there exist non-negative integers ? and ? such that |Si ? Sj | = ? for any two adjacent vertices i and j, and |Si ? Sj | = ? for any two distinct non-adjacent vertices i and j, where Sk denotes the neighborhood of the vertex k. Let ?1 = r, ?2 and ?3 be the distinct eigenvalues of a connected strongly regular graph. Let m1 = 1, m2 and m3 denote the multiplicity of r, ?2 and ?3, respectively. We here describe the parameters n, r, ? and ? for strongly regular graphs with m2 = qm3 and m3 = qm2 for q = 3/2, 4/3, 5/2, 5/3, 5/4, 6/5.

scholarly journals A Prolific Construction of Strongly Regular Graphs with the $n$-e.c. Property

10.37236/1647 ◽  
2002 ◽  
Vol 9 (1) ◽  
Author(s):  
Peter J. Cameron ◽  
Dudley Stark
Keyword(s):  
Regular Graph ◽  
Prime Power ◽  
Probabilistic Methods ◽  
Strongly Regular Graphs ◽  
Regular Graphs ◽  
Existentially Closed ◽  
Large N ◽  
Vertex Set ◽  
Strongly Regular ◽  
Hadamard Designs

A graph is $n$-e.c.$\,$ ($n$-existentially closed) if for every pair of subsets $U$, $W$ of the vertex set $V$ of the graph such that $U\cap W=\emptyset$ and $|U|+|W|=n$, there is a vertex $v\in V-(U\cup W)$ such that all edges between $v$ and $U$ are present and no edges between $v$ and $W$ are present. A graph is strongly regular if it is a regular graph such that the number of vertices mutually adjacent to a pair of vertices $v_1,v_2\in V$ depends only on whether or not $\{v_1,v_2\}$ is an edge in the graph. The only strongly regular graphs that are known to be $n$-e.c. for large $n$ are the Paley graphs. Recently D. G. Fon-Der-Flaass has found prolific constructions of strongly regular graphs using affine designs. He notes that some of these constructions were also studied by Wallis. By taking the affine designs to be Hadamard designs obtained from Paley tournaments, we use probabilistic methods to show that many non-isomorphic strongly regular $n$-e.c. graphs of order $(q+1)^2$ exist whenever $q\geq 16 n^2 2^{2n}$ is a prime power such that $q\equiv 3\!\!\!\pmod{4}$.

scholarly journals On the Clique Number of a Strongly Regular Graph

10.37236/7873 ◽  
2018 ◽  
Vol 25 (4) ◽  
Author(s):  
Gary R. W. Greaves ◽  
Leonard H. Soicher
Keyword(s):  
Regular Graph ◽  
Strongly Regular Graph ◽  
Clique Number ◽  
Upper Bounds ◽  
Strongly Regular Graphs ◽  
Regular Graphs ◽  
Strongly Regular ◽  
Paley Graphs

We determine new upper bounds for the clique numbers of strongly regular graphs in terms of their parameters. These bounds improve on the Delsarte bound for infinitely many feasible parameter tuples for strongly regular graphs, including infinitely many parameter tuples that correspond to Paley graphs.

scholarly journals An example of using star complements in classifying strongly regular graphs

Filomat ◽  
2008 ◽  
Vol 22 (2) ◽  
pp. 53-57 ◽  
Author(s):  
Marko Milosevic
Keyword(s):  
Regular Graph ◽  
Strongly Regular Graph ◽  
Strongly Regular Graphs ◽  
Regular Graphs ◽  
Strongly Regular

In this paper we show how the star complement technique can be used to reprove the result of Wilbrink and Brouwer that the strongly regular graph with parameters (57, 14, 1, 4) does not exist. .

scholarly journals Critical group structure from the parameters of a strongly regular graph

2021 ◽  
Vol 180 ◽  
pp. 105424
Author(s):  
Joshua E. Ducey ◽  
David L. Duncan ◽  
Wesley J. Engelbrecht ◽  
Jawahar V. Madan ◽  
Eric Piato ◽  
...  
Keyword(s):  
Regular Graph ◽  
Group Structure ◽  
Strongly Regular Graph ◽  
Critical Group ◽  
Strongly Regular

scholarly journals Cycle partitions of regular graphs

2020 ◽  
pp. 1-24
Author(s):  
Vytautas Gruslys ◽  
Shoham Letzter
Keyword(s):  
Regular Graph ◽  
Bipartite Graphs ◽  
Disjoint Paths ◽  
Regular Graphs ◽  
Simple Construction ◽  
Vertex Set ◽  
Almost All ◽  
Vertex Disjoint

Abstract Magnant and Martin conjectured that the vertex set of any d-regular graph G on n vertices can be partitioned into $n / (d+1)$ paths (there exists a simple construction showing that this bound would be best possible). We prove this conjecture when $d = \Omega(n)$ , improving a result of Han, who showed that in this range almost all vertices of G can be covered by $n / (d+1) + 1$ vertex-disjoint paths. In fact our proof gives a partition of V(G) into cycles. We also show that, if $d = \Omega(n)$ and G is bipartite, then V(G) can be partitioned into n/(2d) paths (this bound is tight for bipartite graphs).

scholarly journals SPEKTRUM PADA GRAF REGULER KUAT

2013 ◽  
Vol 5 (1) ◽  
pp. 13
Author(s):  
Rizki Mulyani ◽  
Triyani Triyani ◽  
Niken Larasati
Keyword(s):  
Regular Graph ◽  
Adjacency Matrix ◽  
Strongly Regular Graph ◽  
Simple Graph ◽  
Eigen Value ◽  
Strongly Regular

This article studied spectrum of strongly regular graph. This spectrum can be determined by the number of walk with lenght l on connected simple graph, equation of square adjacency matrix and eigen value of strongly regular graph.

scholarly journals There Is No Strongly Regular Graph with Parameters (460, 153, 32, 60)

2018 ◽  
pp. 131-134
Author(s):  
Andriy Bondarenko ◽  
Anton Mellit ◽  
Andriy Prymak ◽  
Danylo Radchenko ◽  
Maryna Viazovska
Keyword(s):  
Regular Graph ◽  
Strongly Regular Graph ◽  
Strongly Regular

On Rank 3 Groups Having λ = 0

1977 ◽  
Vol 29 (4) ◽  
pp. 845-847 ◽  
Author(s):  
M. D. Atkinson
Keyword(s):  
Regular Graph ◽  
Strongly Regular Graph ◽  
Permutation Groups ◽  
Constant Number ◽  
Background Theory ◽  
Strongly Regular

In this paper we shall consider certain rank 3 permutation groups G which act on a set Ω of size n. Thus a point stabiliser Gα will have 3 orbits { α }, △ (α), Γ (α) of sizes 1, k, I respectively. It is well known that, if |G| is even, then the orbital △ defines a strongly regular graph on Ω. In this graph, every point has valency k, every pair of adjacent points are adjacent to a constant number λ of common points, and every pair of non-adjacent points are adjacent to a constant number μ of common points. This notation is reasonably standard (see [4], where much background theory is given).

Sign in / Sign up

Export Citation Format

Share Document