3,437 research outputs found
Metastability and Avalanches in a Nonequilibrium Ferromagnetic System
We present preliminary results on the metastable behavior of a nonequilibrium
ferromagnetic system. The metastable state mean lifetime is a non-monotonous
function of temperature; it shows a maximum at certain non-zero temperature
which depends on the strengh of the nonequilibrium perturbation. This is in
contrast with the equilibrium case in which lifetime increases monotonously as
the temperature is decreasesed. We also report on avalanches during the decay
from the metastable state. Assuming both free boundaries and nonequilibrium
impurities, the avalanches exhibit power-law size and lifetime distributions.
Such scale free behavior is very sensible. The chances are that our
observations may be observable in real (i.e. impure) ferromagnetic
nanoparticles.Comment: 6 pages, 4 figures, to be published in 2002 Granada Seminar
Proceeding
Test of the Additivity Principle for Current Fluctuations in a Model of Heat Conduction
The additivity principle allows to compute the current distribution in many
one-dimensional (1D) nonequilibrium systems. Using simulations, we confirm this
conjecture in the 1D Kipnis-Marchioro-Presutti model of heat conduction for a
wide current interval. The current distribution shows both Gaussian and
non-Gaussian regimes, and obeys the Gallavotti-Cohen fluctuation theorem. We
verify the existence of a well-defined temperature profile associated to a
given current fluctuation. This profile is independent of the sign of the
current, and this symmetry extends to higher-order profiles and spatial
correlations. We also show that finite-time joint fluctuations of the current
and the profile are described by the additivity functional. These results
suggest the additivity hypothesis as a general and powerful tool to compute
current distributions in many nonequilibrium systems.Comment: 4 pages, 4 figure
Simulation of large deviation functions using population dynamics
In these notes we present a pedagogical account of the population dynamics
methods recently introduced to simulate large deviation functions of dynamical
observables in and out of equilibrium. After a brief introduction on large
deviation functions and their simulations, we review the method of Giardin\`a
\emph{et al.} for discrete time processes and that of Lecomte \emph{et al.} for
the continuous time counterpart. Last we explain how these methods can be
modified to handle static observables and extract information about
intermediate times.Comment: Proceedings of the 10th Granada Seminar on Computational and
Statistical Physic
- …