ELASTICITY, FACILITATION, AVALANCHES OF RELAXATION, AND DYNAMIC HETEROGENEITY IN GLASS-FORMING LIQUIDS

We study the role of elasticity-induced facilitation on the dynamics of glass-forming liquids by coarse-grained two-dimensional models in which local relaxation events, taking place by thermal activation, can trigger new relaxations by long-range elastically-mediated interactions. By simulations, we show that the models reproduces the main salient facts associated with dynamic heterogeneity and offers a mechanism to explain the emergence of dynamical correlations at the glass transition [1]. Moreover, we provide a theoretical description of dynamical heterogeneities, based on the premise that relaxation occurs via local rearrangements coupled by elasticity. We find that the dynamical correlation length and correlation volume are controlled by a critical point at vanishing temperature, and predict their singular behavior in terms of the distribution of local energy barriers at T=0. We show that a decoupling between particle diffusion and relaxation time (the so-called Stoke-Einstein violation) must occur, which diverges at T=0. Our description makes a direct connection between dynamical heterogeneities and avalanche-type response [2].