Spatiotemporal correlations of the relaxation rate in glass-forming liquids

Liquids near the glass transition exhibit dynamical heterogeneity, i.e., local relaxation rates fluctuate strongly over space and time. Here, we develop a simple continuum model [1] that allows for quantitative predictions for the time evolution of the heterogeneity. We introduce an algorithm that allows us to extract a correlation function for the relaxation rates, and apply this algorithm to numerical simulation data in model glass forming liquids. This correlation function provides natural definitions for the characteristic size and the lifetime of the heterogeneous regions. We compare the results of this approach with those of alternative ways of defining characteristic lengthscales and timescales for the heterogeneous regions.

[1] R. K. Pandit and H. E. Castillo, PRL 131, 218202 (2023)