title: Subdiffusion and intermittent dynamic fluctuations in the aging regime of concentrated hard spheres.
abstract: We study the nonequilibrium aging dynamics in a system of quasihard spheres at large density by means of computer simulations. We find that, after a sudden quench to large density, the relaxation time initially increases exponentially with the age of the system. After a surprisingly large crossover time, the system enters the asymptotic aging regime characterized by a nearly linear increase in the relaxation time with age. In this aging regime, single-particle motion is strongly non-fickian, with a mean-squared displacement increasing subdiffusively, associated with broad non-gaussian tails in the distribution of particle displacements. We find that the system ages through temporally intermittent relaxation events, and a detailed finite-size analysis of these collective dynamic fluctuations reveals that these events are not spanning the entire system, but remain spatially localized.
authors.affiliation: Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
authors.forename: Djamel
authors.initials: D
authors.lastname: El Masri
authors.forename: Ludovic
authors.initials: L
authors.lastname: Berthier
authors.forename: Luca
authors.initials: L
authors.lastname: Cipelletti