Article ID Journal Published Year Pages File Type
4649551 Discrete Mathematics 2008 4 Pages PDF
Abstract

We introduce two necessary conditions for the existence of graph homomorphisms based on the concepts of density and power graph. As corollaries, we obtain a lower bound for the fractional chromatic number, and we set forward elementary proofs of the facts that the circular chromatic number of the Petersen graph is equal to three and the fact that the Coxeter graph is a core.

Related Topics
Physical Sciences and Engineering Mathematics Discrete Mathematics and Combinatorics
Authors
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