How active forces influence nonequilibrium glass transitions

TL;DR

This paper investigates how active forces affect nonequilibrium glass transitions, revealing that such forces can either fluidify or solidify the system depending on specific conditions, challenging previous assumptions.

Contribution

It introduces a model showing that active forces can both enhance and suppress glassy dynamics, highlighting the complex role of density correlations in nonequilibrium transitions.

Findings

Active forces can both fluidify and depress glassy dynamics.

The transition location is mainly controlled by static density correlations.

Density correlations' dependence on active forces varies non-trivially.

Abstract

Dense assemblies of self-propelled particles undergo a nonequilibrium form of glassy dynamics. Physical intuition suggests that increasing departure from equilibrium due to active forces fluidifies a glassy system. We falsify this belief by devising a model of self-propelled particles where increasing departure from equilibrium can both enhance or depress glassy dynamics, depending on the chosen state point. We analyze a number of static and dynamic observables and suggest that the location of the nonequilibrium glass transition is primarily controlled by the evolution of two-point static density correlations due to active forces. The dependence of the density correlations on the active forces varies non-trivially with the details of the system, and is difficult to predict theoretically. Our results emphasize the need to develop an accurate liquid state theory for nonequilibrium systems.