Many tractable algorithms for solving the Constraint Satisfaction Problem (Csp) have been developed using the notion of the treewidth of some graph derived from the input Csp instance. In particular, the incidence graph of the Csp instance is one such graph. We introduce the notion of an incidence graph for modal logic formulae in a certain normal form. We investigate the parameterized complexi...

Many tractable algorithms for solving the Constraint Satisfaction Problem (Csp) have been developed using the notion of the treewidth of some graph derived from the input Csp instance. In particular, the incidence graph of the Csp instance is one such graph. We introduce the notion of an incidence graph for modal logic formulas in a certain normal form. We investigate the parameterized complexi...

Slovenija Abstract An innnite family of cubic edge-transitive but not vertex-transitive graph graphs with edge stabilizer isomorphic to Z Z 2 is constructed.

Solving a delegation graph for transitive votes is already a non-trivial task for many programmers. When extending the current main paradigm, where each voter can only appoint a single transitive delegation, to a system where each vote can be separated over multiple delegations, solving the delegation graph becomes even harder. This article presents a solution of an example graph, and a non-for...

It is well-known that concentrators are sparse graphs of high connectivity, which play a key role in the construction of switching networks; and any semi-vertex transitive graph is isomorphic to a bi-coset graph. In this paper, we prove that random bi-coset graphs are almost always concentrators, and construct some examples of semi-vertex transitive concentrators.

In this sequel to the paper ‘Arc-transitive abelian regular covers of cubic graphs’, all arc-transitive abelian regular covers of the Heawood graph are found. These covers include graphs that are 1-arc-regular, and others that are 4-arc-regular (like the Heawood graph). Remarkably, also some of these covers are 2-arc-regular.

A special method for construction of transitive orientations of the undirected graph G = (X; U) is proposed. The method uses an iterative procedure for factorization of graph G. Factorization procedure consists in replacing of a B-stable subgraph with a vertex. Transitive orientations are obtained by a polynomial time algorithm which is presented in the paper.

Middendorf, M. and F. Pfeiffer, Weakly transitive orientations, Hasse diagrams and string graphs, Discrete Mathematics 111 (1993) 393-400. We introduce the notion of a weakly transitive orientation for graphs as a natural generalization of transitive orientations and give a characterization for weakly transitive orientations in terms of forbidden substructurs. As a corollary of this characteriz...

A regular and edge-transitive graph which is not vertex-transitive is said to be semisymmetric. Every semisymmetric graph is necessarily bipartite, with the two parts having equal size and the automorphism group acting transitively on each of these parts. A semisymmetric graph is called biprimitive if its automorphism group acts primitively on each part. In this paper biprimitive graphs of smal...

The connective constant μ(G) of a quasi-transitive graph G is the asymptotic growth rate of the number of selfavoiding walks (SAWs) on G from a given starting vertex. We survey several aspects of the relationship between the connective constant and the underlying graph G. • We present upper and lower bounds for μ in terms of the vertex-degree and girth of a transitive graph. • We discuss the qu...