1,644 research outputs found
Polynomial birth--death processes and the second conjecture of Valent
The conjecture of Valent about the type of Jacobi matrices with polynomially
growing weights is proved.Comment: 11 page
Fluctuation theorems for continuously monitored quantum fluxes
It is shown that quantum fluctuation theorems remain unaffected if
measurements of any kind and number of observables are performed during the
action of a force protocol. That is, although the backward and forward
probabilities entering the fluctuation theorems are both altered by these
measurements, their ratio remains unchanged. This observation allows to
describe the measurement of fluxes through interfaces and, in this way, to
bridge the gap between the current theory, based on only two measurements
performed at the beginning and end of the protocol, and experiments that are
based on continuous monitoring.Comment: 4 pages, 1 figure. Accepted in Physical Review Letter
Quantum work relations and response theory
A universal quantum work relation is proved for isolated time-dependent
Hamiltonian systems in a magnetic field as the consequence of
microreversibility. This relation involves a functional of an arbitrary
observable. The quantum Jarzynski equality is recovered in the case this
observable vanishes. The Green-Kubo formula and the Casimir-Onsager reciprocity
relations are deduced thereof in the linear response regime
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
Geometric magnetism in open quantum systems
An isolated classical chaotic system, when driven by the slow change of
several parameters, responds with two reaction forces: geometric friction and
geometric magnetism. By using the theory of quantum fluctuation relations we
show that this holds true also for open quantum systems, and provide explicit
expressions for those forces in this case. This extends the concept of Berry
curvature to the realm of open quantum systems. We illustrate our findings by
calculating the geometric magnetism of a damped charged quantum harmonic
oscillator transported along a path in physical space in presence of a magnetic
field and a thermal environment. We find that in this case the geometric
magnetism is unaffected by the presence of the heat bath.Comment: 7 pages. Signs corrected. v3 Accepted in Phys. Rev.
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
Modeling Maxwell's demon with a microcanonical Szilard engine
Following recent work by Marathe and Parrondo [PRL, 104, 245704 (2010)], we
construct a classical Hamiltonian system whose energy is reduced during the
adiabatic cycling of external parameters, when initial conditions are sampled
microcanonically. Combining our system with a device that measures its energy,
we propose a cyclic procedure during which energy is extracted from a heat bath
and converted to work, in apparent violation of the second law of
thermodynamics. This paradox is resolved by deriving an explicit relationship
between the average work delivered during one cycle of operation, and the
average information gained when measuring the system's energy
Exact Nonequilibrium Work Generating Function for a Small Classical System
We obtain the exact nonequilibrium work generating function (NEWGF), for a
small system consisting of a massive Brownian particle connected to internal
and external springs. The external work is provided to the system for a finite
time interval. The Jarzynski equality (JE), obtained in this case directly from
the NEWGF, is shown to be valid for the present model, in an exact way
regardless of the rate of external work
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