Active Glassy Dynamics is Unaffected by the Microscopic Details of Self-Propulsion

TL;DR

This study shows that in dense active materials, the microscopic details of self-propulsion mechanisms do not significantly affect the long-time glassy dynamics, as demonstrated through theoretical models and simulations.

Contribution

The paper develops a mode-coupling theory for AOUPs and compares it with ABPs, revealing their equivalence in glassy behavior despite different self-propulsion mechanisms.

Findings

AOUP and ABP models produce nearly identical intermediate scattering functions.

Theoretical equivalence between AOUP and ABP models in active glassy dynamics.

Simulations confirm microscopic self-propulsion details do not affect glassy behavior.

Abstract

Recent years have seen a rapid increase of interest in dense active materials, which, in the disordered state, share striking similarities with conventional passive glass-forming matter. For such passive glassy materials, it is well established (at least in three dimensions) that the details of the microscopic dynamics, e.g., Newtonian or Brownian, do not influence the long-time glassy behavior. Here we investigate whether this still holds true in the non-equilibrium active case by considering two simple and widely used active particle models, i.e., active Ornstein-Uhlenbeck particles (AOUPs) and active Brownian particles (ABPs). In particular, we seek to gain more insight into the role of the self-propulsion mechanism on the glassy dynamics by deriving a mode-coupling theory (MCT) for thermal AOUPs, which can be directly compared to a recently developed MCT for ABPs. Both theories explicitly take into account the active degrees of freedom. We solve the AOUP- and ABP-MCT equations in two dimensions and demonstrate that both models give almost identical results for the intermediate scattering function over a large variety of control parameters (packing fractions, active speeds, and persistence times). We also confirm this theoretical equivalence between the different self-propulsion mechanisms numerically via simulations of a polydisperse mixture of active quasi-hard spheres, thereby establishing that, at least for these model systems, the microscopic details of self-propulsion do not alter the active glassy behavior.