Signature of ergodicity in the dynamic response of amorphous systems

We have analyzed dynamical measurements from materials near their liquid-glass transition. The primary response is accurately characterized by a model for dispersive excitations on specific distributions of independently relaxing domains. Liquids have an equilibrium (Gaussian) distribution of domain sizes, which changes abruptly to a locally random (Poisson-like) distribution in the glass. When quenched to a temperature initially in the glass phase, after a definite anneal time, the Poisson-like distribution changes abruptly back to the Gaussian distribution characteristic of a liquid.