Critical behavior of active Brownian particles

TL;DR

This paper investigates the critical behavior of active Brownian particles, introduces a new sampling method for finite-size fluctuations, and finds that their critical exponents differ from the 2D Ising model, suggesting a possible new universality class.

Contribution

It proposes a modified sampling method to accurately locate the critical point of active Brownian particles and explores their critical exponents, revealing potential non-equilibrium universality.

Findings

Critical point at Pe_{cr}=40(2), φ_{cr}=0.597(3)

Critical exponents differ from 2D Ising model

Indicates possible new non-equilibrium universality class

Abstract

We study active Brownian particles as a paradigm for genuine non-equilibrium phase transitions. Access to the critical point in computer simulations is obstructed by the fact that the density is conserved. We propose a modification of sampling finite-size fluctuations and successfully test this method for the 2D Ising model. Using this model allows us to determine accurately the critical point of two dimensional active Brownian particles at $\text{Pe}_{\text{cr}}=40(2)$, $\phi_{\text{cr}}=0.597(3)$. Based on this estimate, we study the corresponding critical exponents $\beta$, $\gamma/\nu$, and $\nu$. Our results are incompatible with the 2D-Ising exponents, thus raising the question whether there exists a corresponding non-equilibrium universality class.