Abstract:
Let G be a simple graph and consider the m-connectivity index (m)chi(G) = Sigma(i1-i2-...-im+1) 1/root d(i1)d(i2)...d(im+1), where i(1) - i(2) - ...- i(m+1) runs over all paths of length m in G and d(i) denotes the degree of the vertex i. We find upper bounds for (m)chi(G) using the eigenvalues of the Laplacian matrix of an associated weighted graph. The method provides also lower bounds for (1)chi(G). (C) 1998 Elsevier Science Inc. All rights reserved.