Tetracyclic harmonic graphs
The algebraic connectivity of two trees connected by an edge of infinite weight.
The alternating sign matrix polytope.
The characteristic polynomial of a graph is reconstructible from the characteristic polynomials of its vertex-deleted subgraphs and their complements.
The classification of edges and the change in multiplicity of an eigenvalue of a real symmetric matrix resulting from the change in an edge value
We take as given a real symmetric matrix A, whose graph is a tree T, and the eigenvalues of A, with their multiplicities. Each edge of T may then be classified in one of four categories, based upon the change in multiplicity of a particular eigenvalue, when the edge is removed (i.e. the corresponding entry of A is replaced by 0).We show a necessary and suficient condition for each possible classification of an edge. A special relationship is observed among 2-Parter edges, Parter edges and singly...
The classification of finite groups by using iteration digraphs
A digraph is associated with a finite group by utilizing the power map defined by for all , where is a fixed natural number. It is denoted by . In this paper, the generalized quaternion and -groups are studied. The height structure is discussed for the generalized quaternion. The necessary and sufficient conditions on a power digraph of a -group are determined for a -group to be a generalized quaternion group. Further, the classification of two generated -groups as abelian or non-abelian...
The combinatorial structure of eventually nonnegative matrices.
The complete product of annihilatingly unique digraphs.
The diameter and Laplacian eigenvalues of directed graphs.
The distance matrix of a bidirected tree.
The enumeration of bit-sequences that satisfy local criteria.
The Estrada Index
The Estrada Index: An Updated Survey
The Euler characteristic of a category.
The fan graph is determined by its signless Laplacian spectrum
Given a graph , if there is no nonisomorphic graph such that and have the same signless Laplacian spectra, then we say that is -DS. In this paper we show that every fan graph is -DS, where and .
The first Dirichlet eigenvalue of bicyclic graphs
In this paper, we have investigated some properties of the first Dirichlet eigenvalue of a bicyclic graph with boundary condition. These results can be used to characterize the extremal bicyclic graphs with the smallest first Dirichlet eigenvalue among all the bicyclic graphs with a given graphic bicyclic degree sequence with minor conditions. Moreover, the extremal bicyclic graphs with the smallest first Dirichlet eigenvalue among all the bicycle graphs with fixed interior vertices of degree...
The inertia of unicyclic graphs and bicyclic graphs
Let G be a graph with n vertices and ν(G) be the matching number of G. The inertia of a graph G, In(G) = (n₊,n₋,n₀) is an integer triple specifying the numbers of positive, negative and zero eigenvalues of the adjacency matrix A(G), respectively. Let η(G) = n₀ denote the nullity of G (the multiplicity of the eigenvalue zero of G). It is well known that if G is a tree, then η(G) = n - 2ν(G). Guo et al. [Ji-Ming Guo, Weigen Yan and Yeong-Nan Yeh. On the nullity and the matching number of unicyclic...
The inverse eigenvalue and inertia problems for minimum rank two graphs.
The Laplacian permanental polynomial for trees
The Laplacian spectral radius of graphs
The Laplacian spectral radius of a graph is the largest eigenvalue of the associated Laplacian matrix. In this paper, we improve Shi's upper bound for the Laplacian spectral radius of irregular graphs and present some new bounds for the Laplacian spectral radius of some classes of graphs.