Stationary dynamics of tracer particles in an elasto-plastic model for the structural relaxation of amorphous solids

摘要: We study numerically, at the mesoscopic level, the structural relaxation of two dimensional disordered systems free from external forces, only subject to temperature activated local plastic rearrangements [1]. The temperature-dependent steady state of our model is characterized by narrower local stress (coarse-grain) distributions and lower average plastic activity as the temperature decreases. This sets the scenario for the development of causal correlations among the plastic events stochastically occurring in the system. To observe this phenomena, we compute the mean square displacement and the dynamical structure factor for tracer particle trajectories in the system during the steady evolution. The relaxation caused by correlated plastic events depend on both length and time scales. At sufficient small time scales we observe a ballistic movement of the tracers, contrasting with a diffusive regime at larger time …