Dynamics of Nonlinear Random Walks on Complex Networks

TL;DR

This paper explores the complex dynamics of nonlinear random walks on networks, revealing how nonlinearity leads to richer behaviors like bifurcations and multistability, extending traditional linear models.

Contribution

It introduces a framework for nonlinear Markov chains on networks, analyzing their stability, bifurcations, and multistability, which was not addressed in prior linear models.

Findings

Existence and uniqueness of stable fixed points in weakly nonlinear regimes.

Identification of period-doubling bifurcations in negative bias regimes.

Discovery of multistability in positive bias regimes.

Abstract

In this paper we study the dynamics of nonlinear random walks. While typical random walks on networks consist of standard Markov chains whose static transition probabilities dictate the flow of random walkers through the network, nonlinear random walks consist of nonlinear Markov chains whose transition probabilities change in time depending on the current state of the system. This framework allows us to model more complex flows through networks that may depend on the current system state. For instance, under humanitarian or capitalistic direction, resource flow between institutions may be diverted preferentially to poorer or wealthier institutions, respectively. Importantly, the nonlinearity in this framework gives rise to richer dynamical behavior than occurs in linear random walks. Here we study these dynamics that arise in weakly and strongly nonlinear regimes in a family of nonlinear random walks where random walkers are biased either towards (positive bias) or away from (negative bias) nodes that currently have more random walkers. In the weakly nonlinear regime we prove the existence and uniqueness of a stable stationary state fixed point provided that the network structure is primitive that is analogous to the stationary distribution of a typical (linear) random walk. We also present an asymptotic analysis that allows us to approximate the stationary state fixed point in the weakly nonlinear regime. We then turn our attention to the strongly nonlinear regime. For negative bias we characterize a period-doubling bifurcation where the stationary state fixed point loses stability and gives rise to a periodic orbit below a critical value. For positive bias we investigate the emergence of multistability of several stable stationary state fixed points.