92 research outputs found
Out-of-equilibrium thermodynamic relations in systems with aging and slow relaxation
The experimental time scale dependence of thermodynamic relations in
out-of-equilibrium systems with aging phenomena is investigated theoretically
by using only aging properties of the two-time correlation functions and the
generalized fluctuation-dissipation theorem (FDT). We show that there are two
experimental time regimes characterized by different thermal properties. In the
first regime where the waiting time is much longer than the measurement time,
the principle of minimum work holds even though a system is out of equilibrium.
In the second regime where both the measurement time and the waiting time are
long, the thermal properties are completely different from properties in
equilibrium. For the single-correlation-scale systems such as -spin
spherical spin-glasses, contrary to a fundamental assumption of thermodynamics,
the work done in an infinitely slow operation depends on the path of change of
the external field even when the waiting time is infinite. On the other hand,
for the multi-correlation-scale systems such as Sherrington-Kirkpatrick model,
the work done in an infinitely slow operation is independent of the path. Our
results imply that in order to describe thermodynamic properties of systems
with aging it is essential to consider the experimental time scales and history
of a system as a state variable is necessary.Comment: 28 pages(REVTeX), 4 figure(EPS). To be published in Phys. Rev.
Measuring the fluctuation-dissipation ratio in glassy systems with no perturbing field
A method is presented for measuring the integrated response in Ising spin
system without applying any perturbing field. Large-scale simulations are
performed in order to show how the method works. Very precise measurements of
the fluctuation-dissipation ratio are presented for 3 different Ising models:
the 2-dimensional ferromagnetic model, the mean-field diluted 3-spin model, and
the 3-dimensional Edwards-Anderson model.Comment: 4 pages, 4 figure
A Dynamical Study of the Quantum p=2 Spherical Model
We present a dynamical study of the disordered quantum p=2 spherical model at
long times. Its phase behavior as a function of spin-bath coupling, strength of
quantum fluctuations and temperature is characterized, and we identify
different paramagnetic and coarsened regions. A quantum critical point at zero
temperature in the limit of vanishing dissipation is also found. Furthermore we
show analytically that the fluctuation-dissipation theorem is obeyed in the
stationary regime.Comment: 13 pages, 4 figures; published versio
Elementary constraints on autocorrelation function scalings
Elementary algebraic constraints on the form of an autocorrelation function
C(tw+t,tw)= rule out some two-time scalings found in the
literature as possible long-time asymptotic forms. The same argument leads to
the realization that two usual definitions of {\em many-time scale} relaxation
for aging systems are not equivalent
Extended droplet theory for aging in short-ranged spin glasses and a numerical examination
We analyze isothermal aging of a four dimensional Edwards-Anderson model in
detail by Monte Carlo simulations. We analyze the data in the view of an
extended version of the droplet theory proposed recently (cond-mat/0202110)
which is based on the original droplet theory plus conjectures on the
anomalously soft droplets in the presence of domain walls. We found that the
scaling laws including some fundamental predictions of the original droplet
theory explain well our results. The results of our simulation strongly suggest
the separation of the breaking of the time translational invariance and the
fluctuation dissipation theorem in agreement with our scenario.Comment: 27 pages, 39 epsfiles, revised versio
Relaxation and overlap probability function in the spherical and mean spherical model
The problem of the equivalence of the spherical and mean spherical models,
which has been thoroughly studied and understood in equilibrium, is considered
anew from the dynamical point of view during the time evolution following a
quench from above to below the critical temperature. It is found that there
exists a crossover time such that for the two
models are equivalent, while for macroscopic discrepancies arise. The
relation between the off equilibrium response function and the structure of the
equilibrium state, which usually holds for phase ordering systems, is found to
hold for the spherical model but not for the mean spherical one. The latter
model offers an explicit example of a system which is not stochastically
stable.Comment: 11 pages, 1 figure, references corrected, to appear in Phys.Rev.
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
Alternate-current dynamic reorganization and nonequilibrium phase transition in driven vortex matter
Externally driven glassy systems may undergo nonequilibrium phase (NEPTs). In particular, ac-driven systems display special features, such as those observed in the vortex matter of NbSe2, where oscillatory drives reorganize the system into partially ordered vortex lattices. We provide experimental evidence for this dynamic reorganization and we show an unambiguous signature of its connection with an NEPT driven by ac forces. We perform a scaling analysis and we estimate critical exponents for this transition. Our results share similarities with some glass-to-viscous-liquid NEPTs and invite a search for similar physics in other elastic disordered media.Fil: Marziali Bermudez, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Cugliandolo, L.F.. Université Pierre et Marie Curie; FranciaFil: Pasquini, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin
Dynamics and thermodynamics of the spherical frustrated Blume-Emery-Griffiths model
We introduce a spherical version of the frustrated Blume-Emery-Griffiths
model and solve exactly the statics and the Langevin dynamics for zero
particle-particle coupling (K=0). In this case the model exhibits an
equilibrium transition from a disordered to a spin glass phase which is always
continuous for nonzero temperature. The same phase diagram results from the
study of the dynamics. Furthermore, we notice the existence of a nonequilibrium
time regime in a region of the disordered phase, characterized by aging as
occurs in the spin glass phase. Due to a finite equilibration time, the system
displays in this region the pattern of interrupted aging.Comment: 19 pages, 8 figure
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