Let G be a graph with n vertices and m edges. Let λ1, λ2, . . . , λn be the eigenvalues of the adjacency matrix of G, and let μ1, μ2, . . . , μn be the eigenvalues of the Laplacian matrix of G. An earlier much studied quantity E(G) = ∑ni=1 |λi | is the energy of the graph G. We now define and investigate the Laplacian energy as LE(G) = ∑ni=1 |μi − 2m/n|. There is a great deal of analogy between...

One of the fundamental properties of a graph is the number of distinct eigenvalues of its adjacency or Laplace matrix. Determining this number is of theoretical interest as well as of practical impact. Sparse graphs with small spectra exhibit excellent structural properties and can act as interconnection topologies. In this paper, for any n we present graphs, for which the product of their vert...

D. Gernert conjectured that the sum of two largest eigenvalues of the adjacency matrix of any simple graph is at most the number of vertices of the graph. This can be proved, in particular, for all regular graphs. Gernert’s conjecture was recently disproved by one of the authors [4], who also provided a nontrivial upper bound for the sum of two largest eigenvalues. In this paper we improve the ...

In this paper we prove that a vertex-centered automorphism of a tree gives a proper factor of the characteristic polynomial of its distance or adjacency matrix. We also show that the characteristic polynomial of the distance matrix of any graph always has a factor of degree equal to the number of vertex orbits of the graph. These results are applied to full k-ary trees and some other problems. ...

Let $G = (V, E)$ be a simple graph. Denote by $D(G)$ the diagonal matrix $diag(d_1,cdots,d_n)$, where $d_i$ is the degree of vertex $i$  and  $A(G)$ the adjacency matrix of $G$. The  signless Laplacianmatrix of $G$ is $Q(G) = D(G) + A(G)$ and the $k-$th signless Laplacian spectral moment of  graph $G$ is defined as $T_k(G)=sum_{i=1}^{n}q_i^{k}$, $kgeqslant 0$, where $q_1$,$q_2$, $cdots$, $q_n$ ...

Our study performed upon an extended series of 28 compounds of 1,2,4-triazole derivatives that demonstrate substantial in vitro antimicrobial activities by serial plate dilution method, using quantitative structure-activity relationship (QSAR) methods that imply analysis of correlations and multiple linear regression (MLR); a significant collection of molecular descriptors was used e.g., Edge a...

A (k,g)-cage is a k-regular simple graph of girth g with minimum possible number vertices. In this paper, (k,g)-cages which are Moore graphs referred as minimal (k,g)-cages. connected called distance regular (DR) if all its vertices have the same intersection array. bipartite biregular (DBR) partite set admit It known that DR and their subdivisions DBR graphs. for we give formula spectral radiu...

We propose a quantum walk defined by digraphs (mixed graphs). This is like Grover that perturbed certain complex-valued function digraphs. The discriminant of this matrix normalization generalized Hermitian adjacency matrices. Furthermore, we give definitions the positive and negative supports transfer matrix, clarify explicit formulas their square. In addition, tables computer on identificatio...

The traditional adjacency matrix of a mixed graph is not symmetric in general, hence its eigenvalues may be real. To overcome this obstacle, several authors have recently defined and studied various Hermitian matrices digraphs or graphs. In work we unify previous offer new perspective on the subject by introducing concept monographs. Moreover, consider questions cospectrality.

Let A(G) denote the adjacency matrix of the graph G. The polynomial pA(G)(x) is usually referred to as the characteristic polynomial of G. For convenience, we use p(G, x) to denote pA(G)(x). The spectrum of a graph G is the set of eigenvalues of A(G) together with their multiplicities. Since A (short for A(G)) is a real symmetric matrix, basic linear algebra tells us a few thing about A and its...