Theory of Aging in Soft Viscoelastic Glasses

Almost all glass-forming materials age; i.e., their rheology and dynamical properties depend on the amount of time spent waiting before a measurement is taken. Thus, there is a fundamental interest in understanding aging in soft glassy materials, which also applies to biological matter such as biocondensates. In this talk, we present a theory of aging for viscoelastic glasses that examines the nonequilibrium, protocol-dependent properties of the system. Using random first-order transition theory, we consider the local fluctuations in the driving force to account for the glassy material's heterogeneity and non-exponential relaxation rates. Our model demonstrates how the stress response and other mechanical properties vary with age. We also discuss general insights into the physics of aging.