Displaying similar documents to “Locally C n k graphs.”

The perfection and recognition of bull-reducible Berge graphs

Hazel Everett, Celina M. H. de Figueiredo, Sulamita Klein, Bruce Reed (2005)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications


The recently announced Strong Perfect Graph Theorem states that the class of perfect graphs coincides with the class of graphs containing no induced odd cycle of length at least 5 or the complement of such a cycle. A graph in this second class is called Berge. A bull is a graph with five vertices x , a , b , c , d and five edges x a , x b , a b , a d , b c . A graph is bull-reducible if no vertex is in two bulls. In this paper we give a simple proof that every bull-reducible Berge graph is perfect. Although this result follows...

Gallai and anti-Gallai graphs of a graph

S. Aparna Lakshmanan, S. B. Rao, A. Vijayakumar (2007)

Mathematica Bohemica


The paper deals with graph operators—the Gallai graphs and the anti-Gallai graphs. We prove the existence of a finite family of forbidden subgraphs for the Gallai graphs and the anti-Gallai graphs to be H -free for any finite graph H . The case of complement reducible graphs—cographs is discussed in detail. Some relations between the chromatic number, the radius and the diameter of a graph and its Gallai and anti-Gallai graphs are also obtained.