Dynamics on the Way to Forming Glass: Bubbles in Space-time

TL;DR

This paper reviews a theoretical framework for understanding the glass transition based on the structure of trajectory space, emphasizing non-equilibrium phase transitions and dynamical heterogeneity in disordered systems.

Contribution

It introduces a novel perspective on glass formation focusing on trajectory space and non-equilibrium phase transitions, extending previous models with molecular dynamics illustrations.

Findings

Identification of dynamical heterogeneity and facilitation as key features

Discovery of non-equilibrium phase transitions in trajectory space

Application of the theory to realistic atomistic models

Abstract

We review a theoretical perspective of the dynamics of glass forming liquids and the glass transition. It is a perspective we have developed with our collaborators during this decade. It is based upon the structure of trajectory space. This structure emerges from spatial correlations of dynamics that appear in disordered systems as they approach non-ergodic or jammed states. It is characterized in terms of dynamical heterogeneity, facilitation and excitation lines. These features are associated with a newly discovered class of non-equilibrium phase transitions. Equilibrium properties have little if anything to do with it. The broken symmetries of these transitions are obscure or absent in spatial structures, but they are vivid in space-time (i.e., trajectory space). In our view, the glass transition is an example of this class of transitions. The basic ideas and principles we review were originally developed through the analysis of idealized and abstract models. Nevertheless, the central ideas are easily illustrated with reference to molecular dynamics of more realistic atomistic models, and we use that illustrative approach here.