SIGNLESS LAPLACIAN SPECTRAL MOMENTS OF GRAPHS AND ORDERING SOME GRAPHS WITH RESPECT TO THEM

چکیده مقاله

Let G = (V,E) be a simple graph. Denote by D(G) the diagonal matrix diag(d1, d_2, ... , d_n) where d_i is the degree of vertex i and A(G) the adjacency matrix of G. The signless Laplacian matrix of G is Q(G) = D(G) + A(G) and the k−th signless Laplacian spectral moment of graph G is defined as sum of q^k for i=1,2,...,n , k > 0, where q_1,q_2, ... , q_n are the eigenvalues of the signless Laplacian matrix of G. In this paper we first compute the k−th signless Laplacian spectral moments of a graph for small k and then we order some graphs with respect to the signless Laplacian spectral moments.