646 research outputs found
Aging effects and dynamic scaling in the 3d Edwards-Anderson spin glasses: a comparison with experiments
We present a detailed study of the scaling behavior of correlations functions
and AC susceptibility relaxations in the aging regime in three dimensional spin
glasses. The agreement between simulations and experiments is excellent
confirming the validity of the full aging scenario with logarithmic corrections
which manifests as weak sub-aging effects.Comment: 6 pages, 6 figures. Previously appeared as a part of cond-mat/000554
A morphological study of cluster dynamics between critical points
We study the geometric properties of a system initially in equilibrium at a
critical point that is suddenly quenched to another critical point and
subsequently evolves towards the new equilibrium state. We focus on the
bidimensional Ising model and we use numerical methods to characterize the
morphological and statistical properties of spin and Fortuin-Kasteleyn clusters
during the critical evolution. The analysis of the dynamics of an out of
equilibrium interface is also performed. We show that the small scale
properties, smaller than the target critical growing length with the dynamic exponent, are characterized by equilibrium at the
working critical point, while the large scale properties, larger than the
critical growing length, are those of the initial critical point. These
features are similar to what was found for sub-critical quenches. We argue that
quenches between critical points could be amenable to a more detailed
analytical description.Comment: 26 pages, 13 figure
Phase separation and critical percolation in bidimensional spin-exchange models
Binary mixtures prepared in an homogeneous phase and quenched into a
two-phase region phase-separate via a coarsening process whereby domains of the
two phases grow in time. With a numerical study of a spin-exchange model we
show that this dynamics first takes a system with equal density of the two
species to a critical percolation state. We prove this claim and we determine
the time-dependence of the growing length associated to this process with the
scaling analysis of the statistical and morphological properties of the
clusters of the two phases.Comment: 6 pages, 9 figure
Persistence in the two dimensional ferromagnetic Ising model
We present very accurate numerical estimates of the time and size dependence
of the zero-temperature local persistence in the ferromagnetic Ising
model. We show that the effective exponent decays algebraically to an
asymptotic value that depends upon the initial condition. More
precisely, we find that takes one universal value for
initial conditions with short-range spatial correlations as in a paramagnetic
state, and the value for initial conditions with the long-range
spatial correlations of the critical Ising state. We checked universality by
working with a square and a triangular lattice, and by imposing free and
periodic boundary conditions. We found that the effective exponent suffers from
stronger finite size effects in the former case.Comment: v2: minor corrections and typos correcte
Dynamical AC study of the critical behavior in Heisenberg spin glasses
We present some numerical results for the Heisenberg spin-glass model with
Gaussian interactions, in a three dimensional cubic lattice. We measure the AC
susceptibility as a function of temperature and determine an apparent finite
temperature transition which is compatible with the chiral-glass temperature
transition for this model. The relaxation time diverges like a power law
with and . Although our
data indicates that the spin-glass transition occurs at the same temperature as
the chiral glass transition, we cannot exclude the possibility of a chiral-spin
coupling scenario for the lowest frequencies investigated.Comment: 7 pages, 4 figure
Slicing the Ising model: critical equilibrium and coarsening dynamics
We study the evolution of spin clusters on two dimensional slices of the
Ising model in contact with a heat bath after a sudden quench to a subcritical
temperature. We analyze the evolution of some simple initial configurations,
such as a sphere and a torus, of one phase embedded into the other, to confirm
that their area disappears linearly in time and to establish the temperature
dependence of the prefactor in each case. Two generic kinds of initial states
are later used: equilibrium configurations either at infinite temperature or at
the paramagnetic-ferromagnetic phase transition. We investigate the
morphological domain structure of the coarsening configurations on slices
of the system, comparing with the behavior of the bidimensional model.Comment: 12 page
Critical percolation in the dynamics of the 2d ferromagnetic Ising model
We study the early time dynamics of the 2d ferromagnetic Ising model
instantaneously quenched from the disordered to the ordered, low temperature,
phase. We evolve the system with kinetic Monte Carlo rules that do not conserve
the order parameter. We confirm the rapid approach to random critical
percolation in a time-scale that diverges with the system size but is much
shorter than the equilibration time. We study the scaling properties of the
evolution towards critical percolation and we identify an associated growing
length, different from the curvature driven one. By working with the model
defined on square, triangular and honeycomb microscopic geometries we establish
the dependence of this growing length on the lattice coordination. We discuss
the interplay with the usual coarsening mechanism and the eventual fall into
and escape from metastability.Comment: 67 pages, 33 figure
How soon after a zero-temperature quench is the fate of the Ising model sealed?
We study the transient between a fully disordered initial condition and a
percolating structure in the low-temperature non-conserved order parameter
dynamics of the bi-dimensional Ising model. We show that a stable structure of
spanning clusters establishes at a time . Our
numerical results yield for the square and kagome,
for the triangular and for the bowtie-a
lattices.We generalise the dynamic scaling hypothesis to take into account this
new time-scale. We discuss the implications of these results for other
non-equilibrium processes.Comment: 5 pages, 6 figures + supplemental material (2 pages, 1 figure),
version 2: new co-author, extended manuscrip
- …