Groupe d’études et de recherche en analyse des décisions


Bounds on the Index of the Signless Laplacian of a Graph

, , et

Let be a simple, undirected graph of order and size with vertex set , edge set , adjacency matrix and vertex degrees . The average degree of the neighbor of vertex is . Let be the diagonal matrix of degrees of . Then is the Laplacian matrix of and the signless Laplacian matrix of . Let denote the index of and the index of . We survey upper bounds on and given in terms of the and , as well as of the numbers of common neighbors of pairs of vertices. It is well known that . We show that many but not all upper bounds on are still valid for .

, 14 pages

Ce cahier a été révisé en avril 2008