A random first-order transition theory for an active glass

Abstract

How does nonequilibrium activity modify the approach to a glass? This is an important question, since many experiments reveal the near-glassy nature of the cell interior, remodeled by activity. However, different simulations of dense assemblies of active particles, parametrized by a self-propulsion force, [Formula: see text], and persistence time, [Formula: see text], appear to make contradictory predictions about the influence of activity on characteristic features of glass, such as fragility. This calls for a broad conceptual framework to understand active glasses; here, we extend the random first-order transition (RFOT) theory to a dense assembly of self-propelled particles. We compute the active contribution to the configurational entropy through an effective model of a single particle in a caging potential. This simple active extension of RFOT provides excellent quantitative fits to existing simulation results. We find that whereas [Formula: see text] always inhibits glassiness, the effect of [Formula: see text] is more subtle and depends on the microscopic details of activity. In doing so, the theory automatically resolves the apparent contradiction between the simulation models. The theory also makes several testable predictions, which we verify by both existing and new simulation data, and should be viewed as a step toward a more rigorous analytical treatment of active glass.

Stationary superstatistics distributions of trapped run-and-tumble particles

“…[24] for active Brownian particles confined in an acoustic trap), corresponding evidently to non-Boltzmann-Gibbs distributions [28,29]. Such non-Boltzmann-Gibbs distributions have also been observed experimentally in optically trapped passive Brownian particles coupled to a bath of active ones [30], in theoretically described tracer particles diffusing in an elastic active gel [31], and in a model of active glasses [32], which manifestly exhibits the intrinsic nonequilibrium nature of active baths.…”

Activated Escape of a Self-Propelled Particle from a Metastable State

“…Activated escapes from metastable states play a major role in a host of physical phenomena, with applications in fields as diverse as biology, chemistry, and astrophysics [1,2]. They also play an important role in active matter, where they control nucleation in motility-induced phase separation [3], activated events in glassy selfpropelled-particle systems [4,5], or escapes through narrow channels [6]. However, despite recent progress [7,8], little is known about the physics that controls the rare events leading to the escape of an active system from a metastable state.…”

Glassy dynamics of a model of bacterial cytoplasm with metabolic activities

“…In parallel to these simulation efforts, the mean-field theories of the glass transition [30] have been extended for dense SPPs. These theories successfully predict the emergence of glassy dynamics in dense SPPs and explain some of the findings of simulations [25,[31][32][33][34]. Moreover, they describe the violation of the fluctuation dissipation theorem and the emergence of the effective temperature in these systems [31].…”