190 research outputs found
Fluctuation relations and rare realizations of transport observables
Fluctuation relations establish rigorous identities for the nonequilibrium
averages of observables. Starting from a general transport master equation with
time-dependent rates, we employ the stochastic path integral approach to study
statistical fluctuations around such averages. We show how under nonequilibrium
conditions, rare realizations of transport observables are crucial and imply
massive fluctuations that may completely mask such identities. Quantitative
estimates for these fluctuations are provided. We illustrate our results on the
paradigmatic example of a mesoscopic RC circuit.Comment: 4 pages, 3 figures; v2: minor changes, published versio
Electron and Phonon Thermal Waves in Semiconductors: an Application to Photothermal Effects
The electron and phonon temperature distribution function are calculated in
semiconductors. We solved the coupled one-dimensional heat-diffussion equations
in the linear approximation in which the physical parameters on the sample are
independent of the temperature. We also consider the heat flux at the surface
of the semiconductor as a boundary condition for each electron and phonon
systems instead of using a fixed temperature. From this, we obtain an
expression for electron and phonon temperature respectively. The
characterization of the thermal waves properties is duscussed and some
practical procedures for this purpose provide us information about the electron
and phonon thermal parameters.Comment: 12 pages, amstex and amssymb macro package (LaTeX2e edition
Minimal Work Principle and its Limits for Classical Systems
The minimal work principle asserts that work done on a thermally isolated
equilibrium system, is minimal for the slowest (adiabatic) realization of a
given process. This principle, one of the formulations of the second law, is
operationally well-defined for any finite (few particle) Hamiltonian system.
Within classical Hamiltonian mechanics, we show that the principle is valid for
a system of which the observable of work is an ergodic function. For
non-ergodic systems the principle may or may not hold, depending on additional
conditions. Examples displaying the limits of the principle are presented and
their direct experimental realizations are discussed.Comment: 4 + epsilon pages, 1 figure, revte
Fluctuation theorems for stochastic dynamics
Fluctuation theorems make use of time reversal to make predictions about
entropy production in many-body systems far from thermal equilibrium. Here we
review the wide variety of distinct, but interconnected, relations that have
been derived and investigated theoretically and experimentally. Significantly,
we demonstrate, in the context of Markovian stochastic dynamics, how these
different fluctuation theorems arise from a simple fundamental time-reversal
symmetry of a certain class of observables. Appealing to the notion of Gibbs
entropy allows for a microscopic definition of entropy production in terms of
these observables. We work with the master equation approach, which leads to a
mathematically straightforward proof and provides direct insight into the
probabilistic meaning of the quantities involved. Finally, we point to some
experiments that elucidate the practical significance of fluctuation relations.Comment: 48 pages, 2 figures. v2: minor changes for consistency with published
versio
Stochastic deformation of a thermodynamic symplectic structure
A stochastic deformation of a thermodynamic symplectic structure is studied.
The stochastic deformation procedure is analogous to the deformation of an
algebra of observables like deformation quantization, but for an imaginary
deformation parameter (the Planck constant). Gauge symmetries of thermodynamics
and corresponding stochastic mechanics, which describes fluctuations of a
thermodynamic system, are revealed and gauge fields are introduced. A physical
interpretation to the gauge transformations and gauge fields is given. An
application of the formalism to a description of systems with distributed
parameters in a local thermodynamic equilibrium is considered.Comment: 22 pages, revtex preprint style; some notations changed and
references added; some formulas and comments adde
Linear response theory and transient fluctuation theorems for diffusion processes: a backward point of view
On the basis of perturbed Kolmogorov backward equations and path integral
representation, we unify the derivations of the linear response theory and
transient fluctuation theorems for continuous diffusion processes from a
backward point of view. We find that a variety of transient fluctuation
theorems could be interpreted as a consequence of a generalized
Chapman-Kolmogorov equation, which intrinsically arises from the Markovian
characteristic of diffusion processes
Thermal Diffusion of a Two Layer System
In this paper thermal conductivity and thermal diffusivity of a two layer
system is examined from the theoretical point of view. We use the one
dimensional heat diffusion equation with the appropriate solution in each layer
and boundary conditions at the interfaces to calculate the heat transport in
this bounded system. We also consider the heat flux at the surface of the samle
as boundary condition instead of using a fixed tempertaure. From this, we
obtain an expression for the efective thermal diffusivity of the composite
sample in terms of the thermal diffusivity of its constituent materials
whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag
Classical and Thermodynamic work fluctuations
We have studied the nature of classical work () and thermodynamic work
() fluctuations in systems driven out of equilibrium both in transient and
time periodic steady state. As the observation time of trajectory increases, we
show that the number of trajectories which exhibit excursions away from the
typical behaviour i.e., , and dissipated heat
decreases as anticipated for macroscopic time scales. Analytical expressions
for such trajectories are obtained. Trajectory for which may not
correspond to or . The applicability of steady state
fluctuation theorems are discussed in our linear as well as nonlinear models.Comment: Based on the talk presented by Mamata Sahoo at the Condensed Matter
Days-Aug. 2008 held at Viswavarati University, Kolkata. 19 pages, 8 figure
Quantum Fluctuation Relations for the Lindblad Master Equation
An open quantum system interacting with its environment can be modeled under
suitable assumptions as a Markov process, described by a Lindblad master
equation. In this work, we derive a general set of fluctuation relations for
systems governed by a Lindblad equation. These identities provide quantum
versions of Jarzynski-Hatano-Sasa and Crooks relations. In the linear response
regime, these fluctuation relations yield a fluctuation-dissipation theorem
(FDT) valid for a stationary state arbitrarily far from equilibrium. For a
closed system, this FDT reduces to the celebrated Callen-Welton-Kubo formula
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