37 research outputs found
A mathematical theorem as the basis for the second law: Thomson's formulation applied to equilibrium
There are several formulations of the second law, and they may, in principle,
have different domains of validity. Here a simple mathematical theorem is
proven which serves as the most general basis for the second law, namely the
Thomson formulation (`cyclic changes cost energy'), applied to equilibrium.
This formulation of the second law is a property akin to particle conservation
(normalization of the wavefunction). It has been stricktly proven for a
canonical ensemble, and made plausible for a micro-canonical ensemble.
As the derivation does not assume time-inversion-invariance, it is applicable
to situations where persistent current occur. This clear-cut derivation allows
to revive the ``no perpetuum mobile in equilibrium'' formulation of the second
law and to criticize some assumptions which are widespread in literature.
The result puts recent results devoted to foundations and limitations of the
second law in proper perspective, and structurizes this relatively new field of
research.Comment: Revised version. Redundant assumption omitted. Microcanonical
ensemble included. Reference added. 7 pages revte
Breakdown of the Landauer bound for information erasure in the quantum regime
A known aspect of the Clausius inequality is that an equilibrium system
subjected to a squeezing \d S of its entropy must release at least an amount
|\dbarrm Q|=T|\d S| of heat. This serves as a basis for the Landauer
principle, which puts a lower bound for the heat generated by erasure
of one bit of information. Here we show that in the world of quantum
entanglement this law is broken. A quantum Brownian particle interacting with
its thermal bath can either generate less heat or even {\it adsorb} heat during
an analogous squeezing process, due to entanglement with the bath. The effect
exists even for weak but fixed coupling with the bath, provided that
temperature is low enough. This invalidates the Landauer bound in the quantum
regime, and suggests that quantum carriers of information can be much more
efficient than assumed so far.Comment: 13 pages, revtex, 2 eps figure
Green function Retrieval and Time-reversal in a Disordered World
We apply the theory of multiple wave scattering to two contemporary, related
topics: imaging with diffuse correlations and stability of time-reversal of
diffuse waves, using equipartition, coherent backscattering and frequency
speckles as fundamental concepts.Comment: 1 figur
Pascal Principle for Diffusion-Controlled Trapping Reactions
"All misfortune of man comes from the fact that he does not stay peacefully
in his room", has once asserted Blaise Pascal. In the present paper we evoke
this statement as the "Pascal principle" in regard to the problem of survival
of an "A" particle, which performs a lattice random walk in presence of a
concentration of randomly moving traps "B", and gets annihilated upon
encounters with any of them. We prove here that at sufficiently large times for
both perfect and imperfect trapping reactions, for arbitrary spatial dimension
"d" and for a rather general class of random walks, the "A" particle survival
probability is less than or equal to the survival probability of an immobile
target in the presence of randomly moving traps.Comment: 4 pages, RevTex, appearing in PR
Chaotic, memory and cooling rate effects in spin glasses: Is the Edwards-Anderson model a good spin glass?
We investigate chaotic, memory and cooling rate effects in the three
dimensional Edwards-Anderson model by doing thermoremanent (TRM) and AC
susceptibility numerical experiments and making a detailed comparison with
laboratory experiments on spin glasses. In contrast to the experiments, the
Edwards-Anderson model does not show any trace of re-initialization processes
in temperature change experiments (TRM or AC). A detailed comparison with AC
relaxation experiments in the presence of DC magnetic field or coupling
distribution perturbations reveals that the absence of chaotic effects in the
Edwards-Anderson model is a consequence of the presence of strong cooling rate
effects. We discuss possible solutions to this discrepancy, in particular the
smallness of the time scales reached in numerical experiments, but we also
question the validity of the Edwards-Anderson model to reproduce the
experimental results.Comment: 17 pages, 10 figures. The original version of the paper has been
split in two parts. The second part is now available as cond-mat/010224
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.
Lattice theory of trapping reactions with mobile species
We present a stochastic lattice theory describing the kinetic behavior of
trapping reactions , in which both the and particles
perform an independent stochastic motion on a regular hypercubic lattice. Upon
an encounter of an particle with any of the particles, is
annihilated with a finite probability; finite reaction rate is taken into
account by introducing a set of two-state random variables - "gates", imposed
on each particle, such that an open (closed) gate corresponds to a reactive
(passive) state. We evaluate here a formal expression describing the time
evolution of the particle survival probability, which generalizes our
previous results. We prove that for quite a general class of random motion of
the species involved in the reaction process, for infinite or finite number of
traps, and for any time , the particle survival probability is always
larger in case when stays immobile, than in situations when it moves.Comment: 12 pages, appearing in PR
Non-Equilibrium Thermodynamic Description of the Coupling between Structural and Entropic Modes in Supercooled Liquids
The density response of supercooled glycerol to an impulsive stimulated
thermal grating (q=0.63 micron^-1) has been studied in the temperature range
(T=200-340 K) where the structure rearrangement (alpha-relaxation) and thermal
diffusion occur on the same time scale. A strong interaction between the two
modes occurs giving rise to a dip in the T-dependence of the apparent thermal
conductivity and a flattening of the apparent alpha-relaxation time upon
cooling. A non-equilibrium thermodynamic (NET) model for the long time response
of relaxing fluids has been developed. The model is capable to reproduce the
experimental data and to explain the observed phenomenology.Comment: to be published in PRE Rapid Commu
Thermodynamics and statistical mechanics of frozen systems in inherent states
We discuss a Statistical Mechanics approach in the manner of Edwards to the
``inherent states'' (defined as the stable configurations in the potential
energy landscape) of glassy systems and granular materials. We show that at
stationarity the inherent states are distributed according a generalized Gibbs
measure obtained assuming the validity of the principle of maximum entropy,
under suitable constraints. In particular we consider three lattice models (a
diluted Spin Glass, a monodisperse hard-sphere system under gravity and a
hard-sphere binary mixture under gravity) undergoing a schematic ``tap
dynamics'', showing via Monte Carlo calculations that the time average of
macroscopic quantities over the tap dynamics and over such a generalized
distribution coincide. We also discuss about the general validity of this
approach to non thermal systems.Comment: 10 pages, 16 figure