239 research outputs found
Growth Kinetics in the N-Component Model. Conserved Order Parameter
We extend the discussion of the growth kinetics of the large-N time-dependent
Ginzburg-Landau model with an order parameter described by a free
energy functional, to the conserved case. Quenches from a high temperature
initial state to a zero temperature state are studied for different selections
of parameters entering the effective potential. In all cases we obtain the
asymptotic form of the structure factor. As expected in analogy with the well
studied model, we find multiscaling behavior whenever stable
equilibrium is reached in the ordering region. On the other hand the present
model also displays a novel feature, namely the occurrence of metastable
relaxation.Comment: 20 pages,Plain Late
Dynamic fluctuations in unfrustrated systems: random walks, scalar fields and the Kosterlitz-Thouless phase
We study analytically the distribution of fluctuations of the quantities
whose average yield the usual two-point correlation and linear response
functions in three unfrustrated models: the random walk, the dimensional
scalar field and the 2d XY model. In particular we consider the time dependence
of ratios between composite operators formed with these fluctuating quantities
which generalize the largely studied fluctuation-dissipation ratio, allowing us
to discuss the relevance of the effective temperature notion beyond linear
order. The behavior of fluctuations in the aforementioned solvable cases is
compared to numerical simulations of the 2d clock model with states.Comment: 27 pages, 3 figure
Out of equilibrium dynamics of the spiral model
We study the relaxation of the bi-dimensional kinetically constrained spiral
model. We show that due to the reversibility of the dynamic rules any unblocked
state fully decorrelates in finite times irrespectively of the system being in
the unjammed or the jammed phase. In consequence, the evolution of any
unblocked configuration occurs in a different sector of phase space from the
one that includes the equilibrium blocked equilibrium configurations at
criticality and in the jammed phase. We argue that such out of equilibrium
dynamics share many points in common with coarsening in the one-dimensional
Ising model and we identify the coarsening structures that are, basically,
lines of vacancies. We provide evidence for this claim by analyzing the
behaviour of several observables including the density of particles and
vacancies, the spatial correlation function, the time-dependent persistence and
the linear response.Comment: 14 pages 12 figure
Complex phase-ordering of the one-dimensional Heisenberg model with conserved order parameter
We study the phase-ordering kinetics of the one-dimensional Heisenberg model
with conserved order parameter, by means of scaling arguments and numerical
simulations. We find a rich dynamical pattern with a regime characterized by
two distinct growing lengths. Spins are found to be coplanar over regions of a
typical size , while inside these regions smooth rotations associated
to a smaller length are observed. Two different and coexisting
ordering mechanisms are associated to these lengths, leading to different
growth laws and violating dynamical
scaling.Comment: 14 pages, 8 figures. To appear on Phys. Rev. E (2009
Heat fluctuations in Ising models coupled with two different heat baths
Monte Carlo simulations of Ising models coupled to heat baths at two
different temperatures are used to study a fluctuation relation for the heat
exchanged between the two thermostats in a time . Different kinetics
(single--spin--flip or spin--exchange Kawasaki dynamics), transition rates
(Glauber or Metropolis), and couplings between the system and the thermostats
have been considered. In every case the fluctuation relation is verified in the
large limit, both in the disordered and in the low temperature phase.
Finite- corrections are shown to obey a scaling behavior.Comment: 5 pages, 2 figures. To be published in Journal of Physics A:
Mathematical and Theoretical as fast track communicatio
Scaling and universality in the aging kinetics of the two-dimensional clock model
We study numerically the aging dynamics of the two-dimensional p-state clock
model after a quench from an infinite temperature to the ferromagnetic phase or
to the Kosterlitz-Thouless phase. The system exhibits the general scaling
behavior characteristic of non-disordered coarsening systems. For quenches to
the ferromagnetic phase, the value of the dynamical exponents, suggests that
the model belongs to the Ising-type universality class. Specifically, for the
integrated response function , we find
consistent with the value found in the two-dimensional
Ising model.Comment: 16 pages, 14 figures (please contact the authors for figures
Energy and Heat Fluctuations in a Temperature Quench
Fluctuations of energy and heat are investigated during the relaxation
following the instantaneous temperature quench of an extended system. Results
are obtained analytically for the Gaussian model and for the large model
quenched below the critical temperature . The main finding is that
fluctuations exceeding a critical threshold do condense. Though driven by a
mechanism similar to that of Bose-Einstein condensation, this phenomenon is an
out-of-equilibrium feature produced by the breaking of energy equipartition
occurring in the transient regime. The dynamical nature of the transition is
illustrated by phase diagrams extending in the time direction.Comment: To be published in the Proceedings of the Research Program "Small
system non equilibrium fluctuations, dynamics and stochastics, and anomalous
behavior", Kavli Institute for Theoretical Physics China, July 2013. 40
pages, 9 figure
Fluctuations of two-time quantities and time-reparametrization invariance in spin-glasses
This article is a contribution to the understanding of fluctuations in the
out of equilibrium dynamics of glassy systems. By extending theoretical ideas
based on the assumption that time-reparametrization invariance develops
asymptotically we deduce the scaling properties of diverse high-order
correlation functions. We examine these predictions with numerical tests in a
standard glassy model, the 3d Edwards-Anderson spin-glass, and in a system
where time-reparametrization invariance is not expected to hold, the 2d
ferromagnetic Ising model, both at low temperatures. Our results enlighten a
qualitative difference between the fluctuation properties of the two models and
show that scaling properties conform to the time-reparametrization invariance
scenario in the former but not in the latter.Comment: 17 pages, 5 figure
Reply to a Comment
Reply to the Comment by F. Corberi, E. Lipiello and M. Zannetti
(cond-mat/0211609)
Off equilibrium response function in the one dimensional random field Ising model
A thorough numerical investigation of the slow dynamics in the d=1 random
field Ising model in the limit of an infinite ferromagnetic coupling is
presented. Crossovers from the preasymptotic pure regime to the asymptotic
Sinai regime are investigated for the average domain size, the autocorrelation
function and staggered magnetization. By switching on an additional small
random field at the time tw the linear off equilibrium response function is
obtained, which displays as well the crossover from the nontrivial behavior of
the d=1 pure Ising model to the asymptotic behavior where it vanishes
identically.Comment: 12 pages, 10 figure
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