^{1} Department of Mathematics and Computer Science (IMADA), Faculty of Science, SDU^{2} unknown^{3} Department of Mathematics and Computer Science (IMADA), Faculty of Science, SDU

DOI:

10.1016/j.disc.2014.08.010

Abstract:

For a simple triangle-free k-chromatic graph G with k >= 2 the upper bound m(n-f (k-2)) on the sum Sigma(2)(G) = Sigma(x is an element of V(G))d(2)(x) of the squares of the degrees of G is proved, where n, m, and f(1) are the order of G, the size of G, and the minimum order of a triangle-free l-chromatic graph, respectively. Consequences of this bound are discussed. Moreover, we generalize the upper bound on Ep (G) = Sigma(p)(G) = Sigma(x is an element of V(G))d(x)) for p = 2 to P >= 3. (C) 2014 Elsevier B.V. All rights reserved.