scholarly journals Improved Upper Bounds for the Laplacian Spectral Radius of a Graph

10.37236/522 ◽  
2011 ◽  
Vol 18 (1) ◽  
Author(s):  
Tianfei Wang ◽  
Jin Yang ◽  
Bin Li
Keyword(s):  
Spectral Radius ◽  
Upper Bounds ◽  
Extremal Graphs ◽  
Laplacian Spectral Radius

In this paper, we present three improved upper bounds for the Laplacian spectral radius of graphs. Moreover, we determine all extremal graphs which achieve these upper bounds. Finally, some examples illustrate that the results are best in all known upper bounds in some sense.

TWO SHARP UPPER BOUNDS FOR THE SIGNLESS LAPLACIAN SPECTRAL RADIUS OF GRAPHS

2011 ◽  
Vol 03 (02) ◽  
pp. 185-191 ◽  
Author(s):  
YA-HONG CHEN ◽  
RONG-YING PAN ◽  
XIAO-DONG ZHANG
Keyword(s):  
Spectral Radius ◽  
Upper Bound ◽  
Adjacency Matrix ◽  
Laplacian Matrix ◽  
Upper Bounds ◽  
Extremal Graphs ◽  
Laplacian Spectral Radius ◽  
Signless Laplacian Matrix ◽  
Signless Laplacian Spectral Radius ◽  
Signless Laplacian

The signless Laplacian matrix of a graph is the sum of its degree diagonal and adjacency matrices. In this paper, we present a sharp upper bound for the spectral radius of the adjacency matrix of a graph. Then this result and other known results are used to obtain two new sharp upper bounds for the signless Laplacian spectral radius. Moreover, the extremal graphs which attain an upper bound are characterized.

Bounds for the skew Laplacian spectral radius of oriented graphs

2019 ◽  
Vol 35 (1) ◽  
pp. 31-40 ◽  
Author(s):  
BILAL A. CHAT ◽  
◽  
HILAL A. GANIE ◽  
S. PIRZADA ◽  
◽  
...  
Keyword(s):  
Spectral Radius ◽  
Upper Bound ◽  
Laplacian Matrix ◽  
Upper Bounds ◽  
Extremal Graphs ◽  
Arbitrary Direction ◽  
Laplacian Spectral Radius ◽  
Underlying Graph ◽  
Signless Laplacian Spectral Radius ◽  
Signless Laplacian

We consider the skew Laplacian matrix of a digraph −→G obtained by giving an arbitrary direction to the edges of a graph G having n vertices and m edges. We obtain an upper bound for the skew Laplacian spectral radius in terms of the adjacency and the signless Laplacian spectral radius of the underlying graph G. We also obtain upper bounds for the skew Laplacian spectral radius and skew spectral radius, in terms of various parameters associated with the structure of the digraph −→G and characterize the extremal graphs.

scholarly journals Nordhaus–Gaddum-Type Relations for Arithmetic-Geometric Spectral Radius and Energy

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Yajing Wang ◽  
Yubin Gao
Keyword(s):  
Graph Theory ◽  
Spectral Radius ◽  
Adjacency Matrix ◽  
Upper Bounds ◽  
Simple Graph ◽  
Spectral Graph Theory ◽  
Extremal Graphs ◽  
Spectral Graph ◽  
Vertex Set

Spectral graph theory plays an important role in engineering. Let G be a simple graph of order n with vertex set V=v1,v2,…,vn. For vi∈V, the degree of the vertex vi, denoted by di, is the number of the vertices adjacent to vi. The arithmetic-geometric adjacency matrix AagG of G is defined as the n×n matrix whose i,j entry is equal to di+dj/2didj if the vertices vi and vj are adjacent and 0 otherwise. The arithmetic-geometric spectral radius and arithmetic-geometric energy of G are the spectral radius and energy of its arithmetic-geometric adjacency matrix, respectively. In this paper, some new upper bounds on arithmetic-geometric energy are obtained. In addition, we present the Nordhaus–Gaddum-type relations for arithmetic-geometric spectral radius and arithmetic-geometric energy and characterize corresponding extremal graphs.

scholarly journals Sharp Upper Bounds for the Laplacian Spectral Radius of Graphs

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Houqing Zhou ◽  
Youzhuan Xu
Keyword(s):  
Spectral Radius ◽  
Transient Stability ◽  
Laplacian Matrix ◽  
Schwarz Inequality ◽  
Upper Bounds ◽  
Power Network ◽  
Laplacian Eigenvalue ◽  
Laplacian Spectral Radius ◽  
Wide Range ◽  
Simple Connected Graph

The spectrum of the Laplacian matrix of a network plays a key role in a wide range of dynamical problems associated with the network, from transient stability analysis of power network to distributed control of formations. LetG=(V,E)be a simple connected graph onnvertices and letμ(G)be the largest Laplacian eigenvalue (i.e., the spectral radius) ofG. In this paper, by using the Cauchy-Schwarz inequality, we show that the upper bounds for the Laplacian spectral radius ofG.

scholarly journals The Spectral Radius for a Class of Double-Star-Like Tree Systems with Maximal Degree 4

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yufeng Mao ◽  
Meijin Xu ◽  
Xiaodong Chen ◽  
Yan-Jun Liu ◽  
Kai Li
Keyword(s):  
Spectral Radius ◽  
Transformation Method ◽  
Upper Bounds ◽  
Double Star ◽  
Maximal Degree ◽  
Extremal Graphs ◽  
Second Degree

We mainly study the properties of the 4-double-star-like tree, which is the generalization of star-like trees. Firstly we use graft transformation method to obtain the maximal and minimum extremal graphs of 4-double-star-like trees. Secondly, by the relations between the degree and second degree of vertices in maximal extremal graphs of 4-double-star-like trees we get the upper bounds of spectral radius of 4-double-star-like trees.

Recent results on the majorization theory of graph spectrum and topological index theory

2015 ◽  
Vol 30 ◽  
Author(s):  
Muhuo Liu ◽  
Bolian Liu ◽  
Kinkar Das
Keyword(s):  
Spectral Radius ◽  
Topological Index ◽  
Index Theory ◽  
Degree Sequences ◽  
Extremal Graphs ◽  
Graph Spectrum ◽  
Laplacian Spectral Radius ◽  
Signless Laplacian Spectral Radius ◽  
Signless Laplacian ◽  
Majorization Theorem

Suppose π = (d_1,d_2,...,d_n) and π′ = (d′_1,d′_2,...,d′_n) are two positive non- increasing degree sequences, write π ⊳ π′ if and only if π \neq π′, \sum_{i=1}^n d_i = \sum_{i=1}^n d′_i, and \sum_{i=1}^j d_i ≤ \sum_{i=1}^j d′_i for all j = 1, 2, . . . , n. Let ρ(G) and μ(G) be the spectral radius and signless Laplacian spectral radius of G, respectively. Also let G and G′ be the extremal graphs with the maximal (signless Laplacian) spectral radii in the class of connected graphs with π and π′ as their degree sequences, respectively. If π ⊳ π′ can deduce that ρ(G) < ρ(G′) (respectively, μ(G) < μ(G′)), then it is said that the spectral radii (respectively, signless Laplacian spectral radii) of G and G′ satisfy the majorization theorem. This paper presents a survey to the recent results on the theory and application of the majorization theorem in graph spectrum and topological index theory.

On spectra and spectral radius of Signless Laplacian of power graphs of some finite groups

2020 ◽  
pp. 2150090
Author(s):  
Subarsha Banerjee ◽  
Avishek Adhikari
Keyword(s):  
Spectral Radius ◽  
Finite Groups ◽  
Upper Bounds ◽  
Lower And Upper Bounds ◽  
Laplacian Spectral Radius ◽  
Power Graph ◽  
Signless Laplacian Spectral Radius ◽  
Signless Laplacian ◽  
Extremal Values ◽  
A Finite Group

Let [Formula: see text] denote the power graph of a finite group [Formula: see text]. Let [Formula: see text] denote the Signless Laplacian spectral radius of [Formula: see text]. In this paper, we give lower and upper bounds on [Formula: see text] for any [Formula: see text] and find those graphs for which the extremal values are attained. We give a comparison between the bounds obtained and exact value of [Formula: see text] for any [Formula: see text]. We then find the eigenvalues of [Formula: see text] and give lower and upper bounds on the spectral radius of [Formula: see text]. When [Formula: see text] and [Formula: see text] where [Formula: see text] are primes and [Formula: see text] is a positive integer, we obtain sharper bounds on [Formula: see text]. Finally, we make a conjecture on [Formula: see text] for any [Formula: see text].

LAPLACIAN EIGENVALUES OF GRAPHS WITH GIVEN DOMINATION NUMBER

2009 ◽  
Vol 02 (01) ◽  
pp. 71-76 ◽  
Author(s):  
Lihua Feng ◽  
Guihai Yu ◽  
Xiqin Lin
Keyword(s):  
Spectral Radius ◽  
Domination Number ◽  
Upper Bounds ◽  
Algebraic Connectivity ◽  
Laplacian Spectral Radius ◽  
Laplacian Eigenvalues ◽  
Eigenvalues Of Graphs

In this paper, we study the Laplacian eigenvalues of graphs on n vertices with domination number γ and present upper bounds for the Laplacian spectral radius and algebraic connectivity as well, which improve old results apparently.

scholarly journals Spectral radius and extremal graphs for class of unicyclic graph with pendant vertices

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770713 ◽  
Author(s):  
Lu Zhi ◽  
Meijin Xu ◽  
Xiujuan Liu ◽  
Xiaodong Chen ◽  
Chen Chen ◽  
...  
Keyword(s):  
Spectral Radius ◽  
Upper Bounds ◽  
Unicyclic Graph ◽  
Extremal Graphs ◽  
Unicyclic Graphs

In this article, we research on the spectral radius of extremal graphs for the unicyclic graphs with girth g mainly by the graft transformation and matching and obtain the upper bounds of the spectral radius of unicyclic graphs.

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