The Experts below are selected from a list of 22008 Experts worldwide ranked by ideXlab platform

B L Altshuler - One of the best experts on this subject based on the ideXlab platform.

  • erratum relaxation and persistent oscillations of the order parameter in fermionic condensates phys rev lett 96 097005 2006
    2006
    Co-Authors: Emil A Yuzbashyan, O Tsyplyatyev, B L Altshuler
    Abstract:

    We determine the limiting dynamics of a fermionic condensate following a sudden perturbation for various initial conditions. We demonstrate that possible initial States of the condensate fall into two classes. In the first case, the order parameter asymptotes to a constant value. The approach to a constant is oscillatory with an inverse square root decay. This happens, e.g., when the strength of pairing is abruptly changed while the system is in the paired ground State and more generally for any Nonequilibrium State that is in the same class as the ground State. In the second case, the order parameter exhibits persistent oscillations with several frequencies. This is realized for Nonequilibrium States that belong to the same class as excited stationary States. Our classification of initial States extends the concept of excitation spectrum to Nonequilibrium regime and allows one to predict the evolution without solving equations of motion.

  • relaxation and persistent oscillations of the order parameter in fermionic condensates
    2006
    Co-Authors: Emil A Yuzbashyan, O Tsyplyatyev, B L Altshuler
    Abstract:

    We determine the limiting dynamics of a fermionic condensate following a sudden perturbation for various initial conditions. Possible initial States of the condensate fall into two classes. In the first case, the order parameter asymptotes to a constant value. The approach to a constant is oscillatory with an inverse square root decay. This happens, e.g., when the strength of pairing is abruptly changed while the system is in the paired ground State and more generally for any Nonequilibrium State that is in the same class as the ground State. In the second case, the order parameter exhibits persistent oscillations with several frequencies. This is realized for Nonequilibrium States that belong to the same class as excited stationary States.

Michael R Von Spakovsky - One of the best experts on this subject based on the ideXlab platform.

  • a method for predicting Nonequilibrium thermal expansion using steepest entropy ascent quantum thermodynamics
    2018
    Co-Authors: Ryo Yamada, Michael R Von Spakovsky, W T Reynolds
    Abstract:

    Steepest-entropy-ascent quantum thermodynamics (SEAQT) is an intriguing approach that describes equilibrium and dynamic processes in a self-consistent way. The applicability is limited to mainly gas phases because of a complex eigenstructure (eigenvalues and eigenfunctions) of solid or liquid phases. In this contribution, the SEAQT modeling is extended to a condensed phase by constructing a simplified eigenstructure (so-called pseudo-eigenstructure), and the applicability is demonstrated by calculating the thermal expansion of metallic silver in three cases: (a) at stable equilibrium, (b) along three irreversible paths from an initial Nonequilibrium State to stable equilibrium, and (c) along an irreversible path between two stable equilibrium States. The SEAQT framework with an anharmonic pseudo-eigenstructure predicts reasonable values for equilibrium thermal expansion. For the irreversible cases considered, the SEAQT approach makes it possible to predict the time-dependence of lattice relaxations from the initial State to the final State.

  • steepest entropy ascent quantum thermodynamic modeling of decoherence in two different microscopic composite systems
    2015
    Co-Authors: Sergio Canoandrade, Gian Paolo Beretta, Michael R Von Spakovsky
    Abstract:

    The steepest-entropy-ascent quantum thermodynamic (SEAQT) framework is used to model the decoherence that occurs during the State evolution of two different microscopic composite systems. The test cases are a two-spin- 1 -particle composite system and a particle-photon field composite system like that experimentally studied in cavity quantum electrodynamics. The first system is used to study the characteristics of the nonlinear equation of motion of the SEAQT framework when modeling the State evolution of a microscopic composite system with particular interest in the phenomenon of decoherence. The second system is used to compare the numerical predictions of the SEAQT framework with experimental cavity quantum electrodynamic data available in the literature. For the two different numerical cases presented, the time evolution of the density operator of the composite system as well as that of the reduced operators belonging to the two constituents is traced from an initial Nonequilibrium State of the composite along its relaxation towards stable equilibrium. Results show for both cases how the initial entanglement and coherence is dissipated during the State relaxation towards a State of stable equilibrium.

Emil A Yuzbashyan - One of the best experts on this subject based on the ideXlab platform.

  • erratum relaxation and persistent oscillations of the order parameter in fermionic condensates phys rev lett 96 097005 2006
    2006
    Co-Authors: Emil A Yuzbashyan, O Tsyplyatyev, B L Altshuler
    Abstract:

    We determine the limiting dynamics of a fermionic condensate following a sudden perturbation for various initial conditions. We demonstrate that possible initial States of the condensate fall into two classes. In the first case, the order parameter asymptotes to a constant value. The approach to a constant is oscillatory with an inverse square root decay. This happens, e.g., when the strength of pairing is abruptly changed while the system is in the paired ground State and more generally for any Nonequilibrium State that is in the same class as the ground State. In the second case, the order parameter exhibits persistent oscillations with several frequencies. This is realized for Nonequilibrium States that belong to the same class as excited stationary States. Our classification of initial States extends the concept of excitation spectrum to Nonequilibrium regime and allows one to predict the evolution without solving equations of motion.

  • relaxation and persistent oscillations of the order parameter in fermionic condensates
    2006
    Co-Authors: Emil A Yuzbashyan, O Tsyplyatyev, B L Altshuler
    Abstract:

    We determine the limiting dynamics of a fermionic condensate following a sudden perturbation for various initial conditions. Possible initial States of the condensate fall into two classes. In the first case, the order parameter asymptotes to a constant value. The approach to a constant is oscillatory with an inverse square root decay. This happens, e.g., when the strength of pairing is abruptly changed while the system is in the paired ground State and more generally for any Nonequilibrium State that is in the same class as the ground State. In the second case, the order parameter exhibits persistent oscillations with several frequencies. This is realized for Nonequilibrium States that belong to the same class as excited stationary States.

Mário J. De Oliveira - One of the best experts on this subject based on the ideXlab platform.

  • stochastic thermodynamics and entropy production of chemical reaction systems
    2018
    Co-Authors: Tânia Tomé, Mário J. De Oliveira
    Abstract:

    We investigate the Nonequilibrium stationary States of systems consisting of chemical reactions among molecules of several chemical species. To this end, we introduce and develop a stochastic formulation of Nonequilibrium thermodynamics of chemical reaction systems based on a master equation defined on the space of microscopic chemical States and on appropriate definitions of entropy and entropy production. The system is in contact with a heat reservoir and is placed out of equilibrium by the contact with particle reservoirs. In our approach, the fluxes of various types, such as the heat and particle fluxes, play a fundamental role in characterizing the Nonequilibrium chemical State. We show that the rate of entropy production in the stationary Nonequilibrium State is a bilinear form in the affinities and the fluxes of reaction, which are expressed in terms of rate constants and transition rates, respectively. We also show how the description in terms of microscopic States can be reduced to a description in terms of the numbers of particles of each species, from which follows the chemical master equation. As an example, we calculate the rate of entropy production of the first and second Schlogl reaction models.We investigate the Nonequilibrium stationary States of systems consisting of chemical reactions among molecules of several chemical species. To this end, we introduce and develop a stochastic formulation of Nonequilibrium thermodynamics of chemical reaction systems based on a master equation defined on the space of microscopic chemical States and on appropriate definitions of entropy and entropy production. The system is in contact with a heat reservoir and is placed out of equilibrium by the contact with particle reservoirs. In our approach, the fluxes of various types, such as the heat and particle fluxes, play a fundamental role in characterizing the Nonequilibrium chemical State. We show that the rate of entropy production in the stationary Nonequilibrium State is a bilinear form in the affinities and the fluxes of reaction, which are expressed in terms of rate constants and transition rates, respectively. We also show how the description in terms of microscopic States can be reduced to a description ...

  • stochastic thermodynamics and entropy production of chemical reaction systems
    2018
    Co-Authors: Tânia Tomé, Mário J. De Oliveira
    Abstract:

    We investigate the Nonequilibrium stationary States of systems consisting of chemical reactions among molecules of several chemical species. To this end we introduce and develop a stochastic formulation of Nonequilibrium thermodynamics of chemical reaction systems based on a master equation defined on the space of microscopic chemical States, and on appropriate definitions of entropy and entropy production, The system is in contact with a heat reservoir, and is placed out of equilibrium by the contact with particle reservoirs. In our approach, the fluxes of various types, such as the heat and particle fluxes, play a fundamental role in characterizing the Nonequilibrium chemical State. We show that the rate of entropy production in the stationary Nonequilibrium State is a bilinear form in the affinities and the fluxes of reaction, which are expressed in terms of rate constants and transition rates, respectively. We also show how the description in terms of microscopic States can be reduced to a description in terms of the numbers of particles of each species, from which follows the chemical master equation. As an example, we calculate the rate of entropy production of the first and second Schl\"ogl reaction models.

Th M Nieuwenhuizen - One of the best experts on this subject based on the ideXlab platform.

  • fluctuations of work from quantum subensembles the case against quantum work fluctuation theorems
    2005
    Co-Authors: Armen E Allahverdyan, Th M Nieuwenhuizen
    Abstract:

    We study how Thomson's formulation of the second law of thermodynamics (no work is extracted from an equilibrium ensemble by a cyclic process) emerges in the quantum situation through the averaging over fluctuations of work. The latter concept is carefully defined for an ensemble of quantum systems, the members of which interact with macroscopic sources of work. The approach is based on splitting a mixed quantum ensemble into pure subensembles, which according to quantum mechanics are maximally complete and irreducible. The splitting is done by filtering the outcomes of a measurement process. The approach is corroborated by comparing to relevant experiments in quantum optics. A critical review is given of two other approaches to fluctuations of work proposed in the literature. It is shown that in contrast to those, the present definition (i) is consistent with the physical meaning of the concept of work as mechanical energy lost by the macroscopic sources, or, equivalently, as the average energy acquired by the ensemble; (ii) applies to an arbitrary Nonequilibrium State. There is no direct generalization of the classical work-fluctuation theorem to the proper quantum domain. This implies nonclassical scenarios for the emergence of the second law.

  • steady adiabatic State its thermodynamics entropy production energy dissipation and violation of onsager relations
    2000
    Co-Authors: Armen E Allahverdyan, Th M Nieuwenhuizen
    Abstract:

    A class of statistical systems is considered where different degrees of freedom have well-separated characteristic times, and are described by different temperatures. The stationary State is a Nonequilibrium State with a heat flow. A generalized statistical thermodynamics is constructed and a universal variational principle is proposed. Entropy production and energy dissipation occur at a constant rate. To leading order in the small ratio of the characteristic times, there exists a universal relation between them. Onsager relations in the context of heat transfer are also considered. They are always broken, except close to equilibrium.