Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4649551 | Discrete Mathematics | 2008 | 4 Pages |
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.
Keywords
Related Topics
Physical Sciences and Engineering
Mathematics
Discrete Mathematics and Combinatorics
Authors
Amir Daneshgar, Hossein Hajiabolhassan,