Let G = (V, E) be a simple graph. Denote by D (G) the diagonal matrix of its vertex degrees and by A (G) its adjacency matrix. Then the Laplacian matrix of G is L (G) = D (G) - A (G) and the signless Laplacian matrix of G is Q (G) = D (G) + A (G). In this paper we obtain a lower bound on the second largest signless Laplacian eigenvalue and an upper bound on the smallest signless Laplacian eigenvalue of G. In , Cvetković et al. have given a series of 30 conjectures on Laplacian eigenvalues and signless Laplacian eigenvalues of G (see also ). Here we prove five conjectures. © 2010 Elsevier Inc. All rights reserved.
Das, K. C. (2010). On conjectures involving second largest signless Laplacian eigenvalue of graphs. Linear Algebra and Its Applications, 432(11), 3018–3029. https://doi.org/10.1016/j.laa.2010.01.005