Aging Dynamics is Trivial in Logarithmic Time

Mar 17, 2010, 4:30 PM
Nordita Seminar Room 132:028 (Nordita)

Nordita Seminar Room 132:028



Paolo Sibani


The dynamics of complex systems collectively known as glassy shares important phenomenological traits. I.e., a transition is generally observed from a time-homogeneous dynamical regime to an aging regime where physical changes occur intermittently and, on average, at a decreasing rate. It has been suggested that a global change of the independent time variable to its logarithm may render the aging dynamics homogeneous and thus trivialize it. In the talk this behavior is shown for experimental data from colloidal systems: the mean square displacement grows linearly in time at low densities but linearly in the logarithm of time at high densities. The intermittent nature of spatial fluctuations and the persistency of particle pairs is also discussed. A phenomenological one-parameter family of models is introduced which relies on the growth and collapse of strongly correlated clusters (“dynamic heterogeneities”). The full spectrum of colloidal behaviors is reperoduced by the model. In the limit where large clusters dominate the dynamics, intermittency induced by record-size events occurs with rate ∝ 1/t, implying a homogeneous, log-Poissonian process that qualitatively reproduces the experimental results. The crucial importance of record-size fluctuations for colloidal dynamics is emphasized.

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