Speaker
Paolo Sibani
Description
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.
