# Active glasses

## TL;DR

Active glasses are a new class of non-equilibrium soft matter combining active particle motion with glass-like behavior, with recent advances in experiments, simulations, and theories revealing their complex dynamics and open questions.

## Contribution

This review synthesizes recent experimental, numerical, and theoretical developments in understanding active glassy matter, highlighting its unique non-equilibrium properties.

## Key findings

- Active glasses exhibit dynamical slowdown and heterogeneity.
- Violation of the Stokes-Einstein relation observed in active glasses.
- Open questions include the nature of aging and fragility in active glassy systems.

## Abstract

Active glassy matter has recently emerged as a novel class of non-equilibrium soft matter, combining energy-driven, active particle movement with dense and disordered glass-like behavior. Here we review the state-of-the-art in this field from an experimental, numerical, and theoretical perspective. We consider both non-living and living active glassy systems, and discuss how several hallmarks of glassy dynamics (dynamical slowdown, fragility, dynamical heterogeneity, violation of the Stokes-Einstein relation, and aging) are manifested in such materials. We start by reviewing the recent experimental evidence in this area of research, followed by an overview of the main numerical simulation studies and physical theories of active glassy matter. We conclude by outlining several open questions and possible directions for future work.