Combinatorics and Graph Theory

1308 Submissions

[2] viXra:1308.0037 [pdf] submitted on 2013-08-06 19:55:15

Smarandache Multi-Spaces & Combinatorial Mathematics

Authors: Linfan Mao
Comments: 73 Pages.

A Smarandache multi-space is a union of n different spaces equipped with some different structures, for an integer n≧2.
Category: Combinatorics and Graph Theory

[1] viXra:1308.0030 [pdf] submitted on 2013-08-05 21:42:13

Estrada Index of Graphs

Authors: Mohammed Kasim, Fumao Zhang, Qiang Wang
Comments: 6 Pages.

Suppose $G$ is a simple graph. The eigenvalues $\delta_1, \delta_2,\ldots, \delta_n$ of $G$ are the eigenvalues of its adjacency matrix $A$. The Estrada index of the graph $G$ is defined as $EE = EE(G) = \Sigma_{i=1}^{n} e^{\delta_i}$. In this paper the basic properties of $EE$ are investigated. Moreover, some lower and upper bounds for the Estrada index in terms of the number of vertices, edges and the Randic index are obtained. In addition, some relations between $EE$ and graph energy $E(G)$ are presented.
Category: Combinatorics and Graph Theory