6 research outputs found
Coarsening on percolation clusters: out-of-equilibrium dynamics versus non linear response
We analyze the violations of linear fluctuation-dissipation theorem (FDT) in
the coarsening dynamics of the antiferromagnetic Ising model on percolation
clusters in two dimensions. The equilibrium magnetic response is shown to be
non linear for magnetic fields of the order of the inverse square root of the
number of sites. Two extreme regimes can be identified in the thermoremanent
magnetization: (i) linear response and out-of-equilibrium relaxation for small
waiting times (ii) non linear response and equilibrium relaxation for large
waiting times. The function characterizing the deviations from linear
FDT cross-overs from unity at short times to a finite positive value for longer
times, with the same qualitative behavior whatever the waiting time. We show
that the coarsening dynamics on percolation clusters exhibits stronger
long-term memory than usual euclidian coarsening.Comment: 17 pages, 10 figure
Time decay of the remanent magnetization in the spin glass model at T=0
Using the zero-temperature Metropolis dynamics, the time decay of the
remanent magnetization in the Edward-Anderson spin glass model with a
uniform random distribution of ferromagnetic and antiferromagnetic interactions
has been investigated. Starting from the saturation, the magnetization per spin
reveals a slow decrease with time, which can be approximated by a power
law:, . Moreover, its
relaxation does not lead it into one of the ground states, and therefore the
system is trapped in metastable isoenergetic microstates remaining magnetized.
Such behaviour is discussed in terms of a random walk the system performs on
its available configuration space.Comment: 9 pages, 3 figure
How glasses explore configuration space
We review a statistical picture of the glassy state derived from the analysis
of the off-equilibrium fluctuation-dissipation relations. We define an
ultra-long time limit where ``one time quantities'' are close to equilibrium
while response and correlation can still display aging.
In this limit it is possible to relate the fluctuation-response relation to
static breaking of ergodicity. The resulting picture suggests that even far
from that limit, the fluctuation-dissipation ratio relates to the rate of
growth of the configurational entropy with free-energy density.Comment: To appear in the proceedings of the "3rd workshop on non-equilibrium
phenomena in supercooled fluids, glasses and amorphous materials" Pisa 22-27
September 200