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Chromatic Relatedness of Graphs

Gerhard Benadé1, Izak Broere1
1Department of Mathematics Rand Afrikaans University Johannesburg SOUTH AFRICA

Abstract

The F-free chromatic number χ(M:F) of a graph M is defined as the least number of classes in a partition of the vertices of M such that F does not occur as an induced subgraph in the subgraph induced by any of the colour classes. Two graphs G and H are called chromatically related if, for each positive integer k, there exists a graph M such that χ(M:G)=χ(M:H)=k, and distantly related whenever a chain of such relatednesses exists between them. Using a basic theorem of Folkman [3], we show that every two graphs on at least two vertices are distantly related.