Article history: Received 21 December 2012 Received in revised form 11 November 2013 Accepted 14 November 2013 Available online 12 December 2013 Communicated by Igor Shparlinski

Motivated from an example of ridge graphs relating to metric polytopes, a class of connected regular graphs such that the squares of their adjacency matrices are in certain symmetric Bose-Mesner algebras of dimension 3 is considered in this paper as a generalization of strongly regular graphs. In addition to analysis of this prototype example defined over ðMetP5Þ , some general properties of th...

It is useful to run computational experiments for many discrete mathematics problems. Many of the remaining open problems require computational resources beyond that of a single researcher. Distributed computing is a way to share computing resources. This work implements a library that provides the features of distributed computing to researchers in a framework specific to a tree-based search.

Spreads of finite symplectic, orthogonal and unitary vector spaces are used to construct new strongly regular graphs having the same parameters as the perpendicularity graphs of the underlying vector spaces. Some of the graphs are. related to partial geometries, while others produce interesting symmetric designs.

Very often, strongly regular graphs appear associated with partial geometries. The point graph of a partial geometry is the graph whose vertices are the points of the geometry and adjacency is defined by collinearity. It is well known that the point graph associated to a partial geometry is a strongly regular graph and, in this case, the strongly regular graph is named geometric. When the param...

We consider directed strongly regular graphs de2ned in 1988 by Duval. All such graphs with n vertices, n6 20, having a vertex-transitive automorphism group, are determined with the aid of a computer. As a consequence, we prove the existence of directed strongly regular graphs for three feasible parameter sets listed by Duval. For one parameter set a computer-free proof of the nonexistence is pr...