Epidemic Outbreaks on Quenched Scale-Free Networks

TL;DR

This paper develops a finite-size scaling theory for epidemic outbreaks with immunity on uncorrelated scale-free networks, revealing a mean-field phase transition and critical behavior.

Contribution

It introduces a finite-size scaling framework for a contact process with immunity on scale-free networks, connecting epidemic thresholds to percolation theory.

Findings

Critical threshold remains finite on scale-free networks.

The epidemic transition follows mean-field universality.

The theory aligns with simulation results.

Abstract

We present a finite-size scaling theory of a contact process with permanent immunity on uncorrelated scale-free networks. We model an epidemic outbreak by an analog of the susceptible-infected-removed model where an infected individual attacks only one susceptible in a time unit in a way we can expect a non-vanishing critical threshold at scale-free networks. As we already know, the susceptible-infected-removed model can be mapped in a bond percolation process, allowing us to compare the critical behavior of site and bond universality classes on networks. We used the external field finite-scale theory, where the dependence on the finite size enters the external field defined as the initial number of infected individuals. We can impose the scale of the external field as $N^{-1}$. The system presents an epidemic-endemic phase transition where the critical behavior obeys the mean-field universality class, as we show theoretically and by simulations.