Non-equilibrium dynamics of spin facilitated glass models

TL;DR

This paper investigates the non-equilibrium aging dynamics of spin facilitated glass models, combining theoretical analysis and numerical simulations to reveal complex aging behaviors and fluctuation-dissipation ratio violations.

Contribution

It provides new analytical and numerical insights into the aging dynamics of kinetically constrained models, especially the Fredrickson-Andersen and East models, across various dimensions.

Findings

Dynamic lengthscales grow during aging.

Negative fluctuation-dissipation ratios are observed.

Models exhibit complex aging behavior despite trivial static properties.

Abstract

We consider the dynamics of spin facilitated models of glasses in the non-equilibrium aging regime following a sudden quench from high to low temperatures. We briefly review known results obtained for the broad class of kinetically constrained models, and then present new results for the behaviour of the one-spin facilitated Fredrickson-Andersen and East models in various spatial dimensions. The time evolution of one-time quantities, such as the energy density, and the detailed properties of two-time correlation and response functions are studied using a combination of theoretical approaches, including exact mappings of master operators and reductions to integrable quantum spin chains, field theory and renormalization group, and independent interval and timescale separation methods. The resulting analytical predictions are confirmed by means of detailed numerical simulations. The models we consider are characterized by trivial static properties, with no finite temperature singularities, but they nevertheless display a surprising variety of dynamic behaviour during aging, which can be directly related to the existence and growth in time of dynamic lengthscales. Well-behaved fluctuation-dissipation ratios can be defined for these models, and we study their properties in detail. We confirm in particular the existence of negative fluctuation-dissipation ratios for a large number of observables. Our results suggest that well-defined violations of fluctuation-dissipation relations, of a purely dynamic origin and unrelated to the thermodynamic concept of effective temperatures, could in general be present in non-equilibrium glassy materials.