Defective Ramsey Numbers and Defective Cocolorings in Some Subclasses of Perfect Graphs

Abstract

In this paper, we investigate a variant of Ramsey numbers called defective Ramsey numbers where cliques and independent sets are generalized to k-dense and k-sparse sets, both commonly called k-defective sets. We focus on the computation of defective Ramsey numbers restricted to some subclasses of perfect graphs. Since direct proof techniques are often insufficient for obtaining new values of defective Ramsey numbers, we provide a generic algorithm to compute defective Ramsey numbers in a given target graph class. We combine direct proof techniques with our efficient graph generation algorithm to compute several new defective Ramsey numbers in perfect graphs, bipartite graphs and chordal graphs. We also initiate the study of a related parameter, denoted by \(c^{{\mathcal {G}}}_k(m)\), which is the maximum order n such that the vertex set of any graph of order n in a class \({\mathcal {G}}\) can be partitioned into at most m subsets each of which is k-defective. We obtain several values for \(c^{{\mathcal {G}}}_k(m)\) in perfect graphs and cographs.