Characterization of extremal graphs from Laplacian eigenvalues and the sum of powers of the Laplacian eigenvalues of graphs
نویسندگان
چکیده
منابع مشابه
On Sum of Powers of the Laplacian and Signless Laplacian Eigenvalues of Graphs
Let G be a graph of order n with signless Laplacian eigenvalues q1, . . . , qn and Laplacian eigenvalues μ1, . . . , μn. It is proved that for any real number α with 0 < α 6 1 or 2 6 α < 3, the inequality qα 1 + · · · + qα n > μ1 + · · · + μn holds, and for any real number β with 1 < β < 2, the inequality q 1 + · · ·+ q n 6 μβ1 + · · ·+ μ β n holds. In both inequalities, the equality is attaine...
متن کاملSome remarks on the sum of the inverse values of the normalized signless Laplacian eigenvalues of graphs
Let G=(V,E), $V={v_1,v_2,ldots,v_n}$, be a simple connected graph with $%n$ vertices, $m$ edges and a sequence of vertex degrees $d_1geqd_2geqcdotsgeq d_n>0$, $d_i=d(v_i)$. Let ${A}=(a_{ij})_{ntimes n}$ and ${%D}=mathrm{diag }(d_1,d_2,ldots , d_n)$ be the adjacency and the diagonaldegree matrix of $G$, respectively. Denote by ${mathcal{L}^+}(G)={D}^{-1/2}(D+A) {D}^{-1/2}$ the normalized signles...
متن کاملA note on sum of powers of the Laplacian eigenvalues of graphs
For a graph G and a real α / = 0, we study the graph invariant sα(G) – the sum of the αth power of the non-zero Laplacian eigenvalues of G. The cases α = 2, 1 2 and −1 have appeared in different problems. Here we establish some properties for sα with α / = 0, 1. We also discuss the cases α = 2, 1 2 . © 2008 Elsevier Inc. All rights reserved. AMS classification: 05C50; 05C90
متن کاملOn the Sum of Powers of Normalized Laplacian Eigenvalues of Graphs
For a graph G without isolated vertices and a real α = 0, we introduce a new graph invariant s∗α (G)the sum of the αth power of the non-zero normalized Laplacian eigenvalues of G. Recently, the cases α = 2 and −1 have appeared in various problems in the literature. Here, we present some lower and upper bounds of s∗α (G) for a connected graph G, where α = 0, 1. We also discuss the case α = −1.
متن کاملSignless Laplacian eigenvalues and circumference of graphs
In this paper, we investigate the relation between the Q -spectrum and the structure of G in terms of the circumference of G. Exploiting this relation, we give a novel necessary condition for a graph to be Hamiltonian by means of its Q -spectrum. We also determine the graphs with exactly one or two Q -eigenvalues greater than or equal to 2 and obtain all minimal forbidden subgraphs and maximal ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 2015
ISSN: 0012-365X
DOI: 10.1016/j.disc.2015.02.006