On the Laplacian Eigenvalues of Signed Graphs

A signed graph is a graph with a sign attached to each edge. This article extends some fundamental concepts of the Laplacian matrices from graphs to signed graphs. In particular, the largest Laplacian eigenvalue of a signed graph is investigated, which generalizes the corresponding results on the largest Laplacian eigenvalue of a graph.     

On the Laplacian Spectrum and Walk-regular Hypergraphs

We use the generalization of the Laplacian matrix to hypergraphs to obtain several spectral-like results on hypergraphs. For instance, we obtain upper bounds on the eccentricity and the excess of any vertex of hypergraphs. We extend to the case of hypergraphs the concepts of walk regularity and spectral regularity, showing that all walk-regular hypergraphs are spectrally-regular. Finally, we obtain an upper bound on the mean distance of walk-regular hypergraphs that involves all the Laplacian spectrum.     

On the Laplacian Spectrum and Walk-regular Hypergraphs

We use the generalization of the Laplacian matrix to hypergraphs to obtain several spectral-like results on hypergraphs. For instance, we obtain upper bounds on the eccentricity and the excess of any vertex of hypergraphs. We extend to the case of hypergraphs the concepts of walk regularity and spectral regularity, showing that all walk-regular hypergraphs are spectrally-regular. Finally, we obtain an upper bound on the mean distance of walk-regular hypergraphs that involves all the Laplacian spectrum.     

Upper Bounds for the Laplacian Graph Eigenvalues

We first apply non-negative matrix theory to the matrix K = D A, where D and A are the degree-diagonal and adjacency matrices of a graph G, respectively, to establish a relation on the largest Laplacian eigenvalue λ1 (G) of G and the spectral radius p(K) of K. And then by using this relation we present two upper bounds for λ1(G) and determine the extremal graphs which achieve the upper bounds.     

Eigenvalues of the negative Laplacian for simply connected bounded domains

This paper is devoted to asymptotic formulae for functions related with the spectrum of the negative Laplacian in two and three dimensional bounded simply connected domains with impedance boundary conditions, where the impedances are assumed to be discontinuous functions. Moreover, asymptotic expressions for the difference of eigenvalues related to the impedance problems with different impedances are derived. Further results may be obtained.     

超图的最优标号与特征值

研究超图的标号性质,首先利用拉普拉斯张量的第二小和最大特征值给出4一致超图的带宽和与割宽的上下界;其次构造与超图对应的简单图,通过其拉普拉斯矩阵的特征值给出超图带宽的下界.     

图的Laplace特征值

简要综述近年来图的Laplace特征值研究的一些进展，并提出若干尚待研究的问题。     

On Riesz Means of Eigenvalues

In this article we prove the equivalence of certain inequalities for Riesz means of eigenvalues of the Dirichlet Laplacian with a classical inequality of Kac. Connections are made via integral transforms including those of Laplace, Legendre, Weyl, and Mellin, and the Riemann–Liouville fractional transform. We also prove new universal eigenvalue inequalities and monotonicity principles for Dirichlet Laplacians as well as certain Schrödinger operators. At the heart of these inequalities are calculations of commutators of operators, sum rules, and monotonic properties of Riesz means. In the course of developing these inequalities we prove new bounds for the partition function and the spectral zeta function (cf. Corollaries 3.5–3.7) and conjecture about additional bounds.     

On the lowest eigenvalue of the Hodge Laplacian on compact,negatively curved domains

We study the first eigenvalue of the Laplacian acting on differential forms on a compact Riemannian domain, for the absolute or relative boundary conditions. We prove a series of lower bounds when the domain is starlike or p-convex and the ambient manifold has pinched negative curvature. The bounds are sharp for starlike domains. We then compute the asymptotics of the first eigenvalue of hyperbolic balls of large radius. Finally, we give lower bounds also for Euclidean domains.      

An eigenvalue bound for the Laplacian of a graph

We present a lower bound for the smallest non-zero eigenvalue of the Laplacian of an undirected graph. The bound is primarily useful for graphs with small diameter.     

On the ordering of trees by the Laplacian coefficients

We generalize the results from [X.-D. Zhang, X.-P. Lv, Y.-H. Chen, Ordering trees by the Laplacian coefficients, Linear Algebra Appl. (2009), doi:10.1016/j.laa.2009.04.018] on the partial ordering of trees with given diameter. For two n-vertex trees T₁ and T₂, if c_k(T₁)c_k(T₂) holds for all Laplacian coefficients c_k,k=0,1,…,n, we say that T₁ is dominated by T₂ and write T_1cT₂. We proved that among n vertex trees with fixed diameter d, the caterpillar C_n,d has minimal Laplacian coefficients c_k,k=0,1,…,n. The number of incomparable pairs of trees on 18 vertices is presented, as well as infinite families of examples for two other partial orderings of trees, recently proposed by Mohar. For every integer n, we construct a chain of n-vertex trees of length , such that T₀S_n,T_mP_n and T_icT_i+1 for all i=0,1,…,m-1. In addition, the characterization of the partial ordering of starlike trees is established by the majorization inequalities of the pendent path lengths. We determine the relations among the extremal trees with fixed maximum degree, and with perfect matching and further support the Laplacian coefficients as a measure of branching.     

Eigenvalues and diameter

Let G be a connected graph of order n. The diameter of a graph is the maximum distance between any two vertices of G. In this paper, we will give some bounds on the diameter of G in terms of eigenvalues of adjacency matrix and Laplacian matrix, respectively.     

The Laplacian energy of random graphs

Gutman et al. introduced the concepts of energy E(G) and Laplacian energy EL(G) for a simple graph G, and furthermore, they proposed a conjecture that for every graph G, E(G) is not more than EL(G). Unfortunately, the conjecture turns out to be incorrect since Liu et al. and Stevanovi? et al. constructed counterexamples. However, So et al. verified the conjecture for bipartite graphs. In the present paper, we obtain, for a random graph, the lower and upper bounds of the Laplacian energy, and show that the conjecture is true for almost all graphs.     

图的二维带宽及其Laplacian特征值

图的二维带宽问题是将图G嵌入平面网格图，并使基于该嵌入的函数取得最优值（通常是最小值）。本文研究了图的二维带宽与其Laplacian特征值之间的关系。     

子图匹配数与图无符号拉普拉斯谱(英文)

设H是图G的一个子图.图G中同构于H的点不交的子图构成的集合称为G的一个H-匹配.图G的H-匹配的最大基数称为是G的H-匹配数,记为ν(H,G).本文主要研究ν(H,G)与G的无符号拉普拉斯谱的关系,同时也讨论了ν(H,G)与G的拉普拉斯谱的关系.     

Lower bounds of the Laplacian spectrum of graphs based on diameter

Let G be a connected graph of order n. The diameter of G is the maximum distance between any two vertices of G. In the paper, we will give some lower bounds for the algebraic connectivity and the Laplacian spectral radius of G in terms of the diameter of G.     

几类图的拉普拉斯特征值的前三项和的上界

设G是一个顶点集为V(G),边集为E(G))的简单图.S_k(G)表示图G的拉普拉斯特征值的前k项部分和.Brouwer et al.给出如下猜想:S_k(G)≤e(G)+((k+1)/2),1≤k≤n.证明了当k=3时,对边数不少于n~2/4-n/4的图及有完美匹配或有6-匹配的图,猜想是正确的.     

Remarks on Spectral Radius and Laplacian Eigenvalues of a Graph

Let G be a graph with n vertices, m edges and a vertex degree sequence (d ₁, d ₂,..., d _n ), where d ₁ ≥ d ₂ ≥ ... ≥ d _n . The spectral radius and the largest Laplacian eigenvalue are denoted by ϱ(G) and μ(G), respectively. We determine the graphs with