Eur. Phys. J. B (2018) 91: 82
https://doi.org/10.1140/epjb/e2018-80560-8

Regular Article

A recursive method for calculating the total number of spanning trees and its applications in self-similar small-world scale-free network models

¹ School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, P.R. China
² School of Software and Microelectronics, Peking University, Beijing 102600, P.R. China
³ College of Mathematics and Statistics, Northwest Normal University, Lanzhou, Gansu 730070, P.R. China
⁴ School of Electronics and Information Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P.R. China

^a e-mail: mafei123987@163.com

Received: 5 October 2017
Received in final form: 5 January 2018
Published online: 17 May 2018

Abstract

The problem of determining and calculating the number of spanning trees of any finite graph (model) is a great challenge, and has been studied in various fields, such as discrete applied mathematics, theoretical computer science, physics, chemistry and the like. In this paper, firstly, thank to lots of real-life systems and artificial networks built by all kinds of functions and combinations among some simpler and smaller elements (components), we discuss some helpful network-operation, including link-operation and merge-operation, to design more realistic and complicated network models. Secondly, we present a method for computing the total number of spanning trees. As an accessible example, we apply this method to space of trees and cycles respectively, and our results suggest that it is indeed a better one for such models. In order to reflect more widely practical applications and potentially theoretical significance, we study the enumerating method in some existing scale-free network models. On the other hand, we set up a class of new models displaying scale-free feature, that is to say, following P(k) ~ k^−γ, where γ is the degree exponent. Based on detailed calculation, the degree exponent γ of our deterministic scale-free models satisfies γ > 3. In the rest of our discussions, we not only calculate analytically the solutions of average path length, which indicates our models have small-world property being prevailing in amounts of complex systems, but also derive the number of spanning trees by means of the recursive method described in this paper, which clarifies our method is convenient to research these models.