Structural fluctuations in active glasses

TL;DR

This paper investigates the structural fluctuations in active glasses composed of self-propelled particles, revealing how active forces influence high-frequency modes and violate equipartition, thus advancing understanding of their solid-state properties.

Contribution

It introduces a formalism for analyzing the solid-state properties of active glasses and uncovers how active forces suppress excitations of high-frequency modes.

Findings

High-frequency normal modes become quasi-static under active forces

Excitations of these modes are significantly suppressed

Active glasses exhibit apparent collective motion

Abstract

The glassy dynamics of dense active matter have recently become a topic of interest due to their importance in biological processes such as wound healing and tissue development. However, while the liquid-state properties of dense active matter have been studied in relation to the glass transition of active matter, the solid-state properties of active glasses have yet to be understood. In this work, we study the structural fluctuations in the active glasses composed of self-propelled particles. We develop a formalism to describe the solid-state properties of active glasses in the harmonic approximation limit and use it to analyze the displacement fields in the active glasses. Our findings reveal that the dynamics of high-frequency normal modes become quasi-static with respect to the active forces, and consequently, excitations of these modes are significantly suppressed. This leads to a violation of the equipartition law, suppression of particle displacements, and the apparent collective motion of active glasses. Overall, our results provide a fundamental understanding of the solid-state properties of active glasses.