Steady-state distributions of probability fluxes on complex networks

TL;DR

This paper analyzes the statistical properties of probability fluxes in complex networks driven out of equilibrium by external forces, showing that their steady-state distributions are normally distributed with a standard deviation related to the flux and external force.

Contribution

It introduces a model of Markovian dynamics with an external transition (gate) on complex networks and demonstrates that flux distributions converge to a normal distribution regardless of network topology.

Findings

Flux distributions are normally distributed under external forcing.

Standard deviation of flux depends on the square root of the average flux.

Network modifications affect flux distribution parameters as predicted theoretically.

Abstract

The methodology based on the random walk processes is adapted and applied to a comprehensive analysis of the statistical properties of the probability fluxes. To this aim we define a simple model of the Markovian stochastic dynamics on a complex network extended by the additional transition, called hereafter the gate. The random skips through the gate, driven by the external constant force, violate the detailed balance in the network. We argue, using a theoretical approach and numerical simulations, that the stationary distributions of the probability fluxes emergent under such conditions converge, regardless of the network topology, to the normal distribution. This result, combined with the stationary fluctuation theorem, permits to show that its standard deviation depends directly on the square root of the average flux. In turn, the central result of our paper relates this quantity to the external constant force and the two parameters that entirely characterize the normal distribution of the probability fluxes both close to as well as far from the equilibrium state. Also, the other effects that modify these parameters, such as the addition of shortcuts to the tree-like network, the extension and configuration of the gate and a change in the network size studied by means of the computer simulations are widely discussed in terms of the rigorous theoretical predictions.