Agent-based neutral competition in two-community networks

TL;DR

This paper studies how community structure and update rules influence neutral competition dynamics in networks, providing a theoretical framework that aligns with simulations and aids predictions even with incomplete data.

Contribution

It introduces a heterogeneous mean-field theory for neutral competition in two-community networks, accounting for various update limitations and validated by Monte Carlo simulations.

Findings

Community structure affects success probabilities of states.

Update rules influence the time to reach consensus.

Mean-field theory accurately predicts competition outcomes.

Abstract

Competition between alternative states is an essential process in social and biological networks. Neutral competition can be represented by an unbiased random drift process in which the states of vertices (e.g., opinions, genotypes, or species) in a network are updated by repeatedly selecting two connected vertices. One of these vertices copies the state of the selected neighbor. Such updates are repeated until all vertices are in the same "consensus" state. There is no unique rule for selecting the vertex pair to be updated. Real-world processes comprise three limiting factors that can influence the selected edge and the direction of spread: (1) the rate at which a vertex sends a state to its neighbors, (2) the rate at which a state is received by a neighbor, and (3) the rate at which a state can be exchanged through a connecting edge. We investigate how these three limitations influence neutral competition in networks with two communities generated by a stochastic block model. By using Monte Carlo simulations, we show how the community structure and update rule determine the states' success probabilities and the time until a consensus is reached. We present a heterogeneous mean-field theory that agrees well with the Monte Carlo simulations. The effectiveness of the heterogeneous mean-field theory implies that quantitative predictions about the consensus are possible even if empirical data (e.g., from ecological fieldwork or observations of social interactions) do not allow a complete reconstruction of all edges in the network.