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Thomas Speck - One of the best experts on this subject based on the ideXlab platform.
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Driven Soft Matter: Entropy Production and the Fluctuation-Dissipation Theorem
Progress of Theoretical Physics Supplement, 2010Co-Authors: Thomas SpeckAbstract:Entropy and the fluctuation-Dissipation Theorem are at the heart of statistical mechanics near equilibrium. Driving a system beyond the linear response regime leads to (i) the breakdown of the fluctuation-Dissipation Theorem and (ii) a nonzero entropy production rate. We show how both phenomena are related using the general framework of stochastic thermodynamics suitable for soft matter systems governed by stochastic dynamics and driven through nonconservative forces or external flows. In particular, the excess of the fluctuation-Dissipation Theorem in a nonequilibrium steady state compared to equilibrium is related to total entropy production. Alternative recent derivations of generalized fluctuationDissipation Theorems are sketched and related to each other. The theory is illustrated for two systems: a driven single colloidal particle and systems driven through simple shear flow.
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Fluctuation-Dissipation Theorem in Nonequilibrium Steady States
EPL (Europhysics Letters), 2010Co-Authors: Udo Seifert, Thomas SpeckAbstract:In equilibrium, the fluctuation-Dissipation Theorem (FDT) expresses the response of an observable to a small perturbation by a correlation function of this variable with another one that is conjugate to the perturbation with respect to \emph{energy}. For a nonequilibrium steady state (NESS), the corresponding FDT is shown to involve in the correlation function a variable that is conjugate with respect to \emph{entropy}. By splitting up entropy production into one of the system and one of the medium, it is shown that for systems with a genuine equilibrium state the FDT of the NESS differs from its equilibrium form by an additive term involving \emph{total} entropy production. A related variant of the FDT not requiring explicit knowledge of the stationary state is particularly useful for coupled Langevin systems. The \emph{a priori} surprising freedom apparently involved in different forms of the FDT in a NESS is clarified.
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fluctuation Dissipation Theorem in nonequilibrium steady states
EPL, 2010Co-Authors: Udo Seifert, Thomas SpeckAbstract:In equilibrium, the fluctuation-Dissipation Theorem (FDT) expresses the response of an observable to a small perturbation by a correlation function of this variable with another one that is conjugate to the perturbation with respect to energy. For a nonequilibrium steady state (NESS), the corresponding FDT is shown to involve in the correlation function a variable that is conjugate with respect to entropy. By splitting up entropy production into one of the system and one of the medium, it is shown that for systems with a genuine equilibrium state the FDT of the NESS differs from its equilibrium form by an additive term involving total entropy production. A related variant of the FDT not requiring explicit knowledge of the stationary state is particularly useful for coupled Langevin systems. The a priori surprising freedom apparently involved in different forms of the FDT in a NESS is clarified.
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Extended fluctuation-Dissipation Theorem for soft matter in stationary flow
Physical Review E, 2009Co-Authors: Thomas Speck, Udo SeifertAbstract:For soft matter systems strongly driven by stationary flow, we discuss an extended fluctuation-Dissipation Theorem (FDT). Beyond the linear-response regime, the FDT for the stress acquires an additional contribution involving the observable that is conjugate to the strain rate with respect to the Dissipation function. This extended FDT is evaluated both analytically for Rouse polymers and in numerical simulations for colloidal suspensions. More generally, our results suggest an extension of Onsager's regression principle to nonequilibrium steady states.
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Restoring a fluctuation-Dissipation Theorem in a nonequilibrium steady state
Europhysics Letters (EPL), 2006Co-Authors: Thomas Speck, Udo SeifertAbstract:In a nonequilibrium steady state, the violation of the fluctuation-Dissipation Theorem (FDT) is connected to breaking detailed balance. For the velocity correlations of a driven colloidal particle we calculate an explicit expression of the FDT violation. The equilibrium form of the FDT can be restored by measuring the velocity with respect to the local mean velocity.
Udo Seifert - One of the best experts on this subject based on the ideXlab platform.
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Fluctuation-Dissipation Theorem in Nonequilibrium Steady States
EPL (Europhysics Letters), 2010Co-Authors: Udo Seifert, Thomas SpeckAbstract:In equilibrium, the fluctuation-Dissipation Theorem (FDT) expresses the response of an observable to a small perturbation by a correlation function of this variable with another one that is conjugate to the perturbation with respect to \emph{energy}. For a nonequilibrium steady state (NESS), the corresponding FDT is shown to involve in the correlation function a variable that is conjugate with respect to \emph{entropy}. By splitting up entropy production into one of the system and one of the medium, it is shown that for systems with a genuine equilibrium state the FDT of the NESS differs from its equilibrium form by an additive term involving \emph{total} entropy production. A related variant of the FDT not requiring explicit knowledge of the stationary state is particularly useful for coupled Langevin systems. The \emph{a priori} surprising freedom apparently involved in different forms of the FDT in a NESS is clarified.
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fluctuation Dissipation Theorem in nonequilibrium steady states
EPL, 2010Co-Authors: Udo Seifert, Thomas SpeckAbstract:In equilibrium, the fluctuation-Dissipation Theorem (FDT) expresses the response of an observable to a small perturbation by a correlation function of this variable with another one that is conjugate to the perturbation with respect to energy. For a nonequilibrium steady state (NESS), the corresponding FDT is shown to involve in the correlation function a variable that is conjugate with respect to entropy. By splitting up entropy production into one of the system and one of the medium, it is shown that for systems with a genuine equilibrium state the FDT of the NESS differs from its equilibrium form by an additive term involving total entropy production. A related variant of the FDT not requiring explicit knowledge of the stationary state is particularly useful for coupled Langevin systems. The a priori surprising freedom apparently involved in different forms of the FDT in a NESS is clarified.
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Extended fluctuation-Dissipation Theorem for soft matter in stationary flow
Physical Review E, 2009Co-Authors: Thomas Speck, Udo SeifertAbstract:For soft matter systems strongly driven by stationary flow, we discuss an extended fluctuation-Dissipation Theorem (FDT). Beyond the linear-response regime, the FDT for the stress acquires an additional contribution involving the observable that is conjugate to the strain rate with respect to the Dissipation function. This extended FDT is evaluated both analytically for Rouse polymers and in numerical simulations for colloidal suspensions. More generally, our results suggest an extension of Onsager's regression principle to nonequilibrium steady states.
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Restoring a fluctuation-Dissipation Theorem in a nonequilibrium steady state
Europhysics Letters (EPL), 2006Co-Authors: Thomas Speck, Udo SeifertAbstract:In a nonequilibrium steady state, the violation of the fluctuation-Dissipation Theorem (FDT) is connected to breaking detailed balance. For the velocity correlations of a driven colloidal particle we calculate an explicit expression of the FDT violation. The equilibrium form of the FDT can be restored by measuring the velocity with respect to the local mean velocity.
N. E. Israeloff - One of the best experts on this subject based on the ideXlab platform.
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Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass
Physical Review Letters, 1999Co-Authors: Tomas S Grigera, N. E. IsraeloffAbstract:The fluctuation-Dissipation Theorem (FDT), connecting dielectric susceptibility and polarization noise, was studied in glycerol below its glass transition temperature ${T}_{g}$. Weak FDT violations were observed after a quench from just above to just below ${T}_{g}$, for frequencies above the $\ensuremath{\alpha}$ peak. Violations persisted up to ${10}^{5}$ times the thermal equilibration time of the configurational degrees of freedom under study, but comparable to the average relaxation time of the material. These results suggest that excess energy flows from slower to faster relaxing modes.
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Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass
Physical Review Letters, 1999Co-Authors: Tomas S Grigera, N. E. IsraeloffAbstract:The fluctuation-Dissipation Theorem (FDT), connecting dielectric susceptibility and polarization noise was studied in glycerol below its glass transition temperature Tg. Weak FDT violations were observed after a quench from just above to just below Tg, for frequencies above the alpha peak. Violations persisted up to 10^5 times the thermal equilibration time of the configurational degrees of freedom under study, but comparable to the average relaxation time of the material. These results suggest that excess energy flows from slower to faster relaxing modes.
Kazuo Fujikawa - One of the best experts on this subject based on the ideXlab platform.
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Fluctuation-Dissipation Theorem and quantum tunneling with Dissipation at finite temperature
Physical Review E, 1998Co-Authors: Kazuo Fujikawa, Hiroaki TerashimaAbstract:A reformulation of the fluctuation-Dissipation Theorem of Callen and Welton is presented in such a manner that the basic idea of Feynman-Vernon and Caldeira -Leggett of using an infinite number of oscillators to simulate the dissipative medium is realized manifestly without actually introducing oscillators. If one assumes the existence of a well defined dissipative coefficient $R(\omega)$ which little depends on the temperature in the energy region we are interested in, the spontanous and induced emissions as well as induced absorption of these effective oscillators with correct Bose distribution automatically appears. Combined with a dispersion relation, we reproduce the tunneling formula in the presence of Dissipation at finite temperature without referring to an explicit model Lagrangian. The fluctuation-Dissipation Theorem of Callen-Welton is also generalized to the fermionic Dissipation (or fluctuation) which allows a transparent physical interpretation in terms of second quantized fermionic oscillators. This fermionic version of fluctuation-Dissipation Theorem may become relevant in the analyses of, for example, fermion radiation from a black hole and also supersymmetry at the early universe.
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Fluctuation-Dissipation Theorem and quantum tunneling with Dissipation
Physical Review E, 1998Co-Authors: Kazuo FujikawaAbstract:We suggest taking the fluctuation-Dissipation Theorem of Callen and Welton [Phys. Rev. 83, 34 (1951)] as a basis to study quantum dissipative phenomena (such as macroscopic quantum tunneling) in a manner analogous to the Nambu-Goldstone Theorem for spontaneous symmetry breakdown [Phys. Rev. 122, 345 (1961); Nuovo Cimento 19, 154 (1961)]. It is shown that the essential physical contents of the Caldeira-Leggett model [Phys. Rev. Lett. 46, 211 (1981); Ann. Phys. (N.Y.) 149, 374 (1983)] such as the suppression of quantum coherence by Ohmic Dissipation are derived from general principles only, namely, the fluctuation-Dissipation Theorem and unitarity and causality (i.e., dispersion relations), without referring to an explicit form of the Lagrangian. An interesting connection between quantum tunneling with Ohmic Dissipation and Anderson's orthogonality Theorem is also noted.
Tomas S Grigera - One of the best experts on this subject based on the ideXlab platform.
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Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass
Physical Review Letters, 1999Co-Authors: Tomas S Grigera, N. E. IsraeloffAbstract:The fluctuation-Dissipation Theorem (FDT), connecting dielectric susceptibility and polarization noise, was studied in glycerol below its glass transition temperature ${T}_{g}$. Weak FDT violations were observed after a quench from just above to just below ${T}_{g}$, for frequencies above the $\ensuremath{\alpha}$ peak. Violations persisted up to ${10}^{5}$ times the thermal equilibration time of the configurational degrees of freedom under study, but comparable to the average relaxation time of the material. These results suggest that excess energy flows from slower to faster relaxing modes.
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Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass
Physical Review Letters, 1999Co-Authors: Tomas S Grigera, N. E. IsraeloffAbstract:The fluctuation-Dissipation Theorem (FDT), connecting dielectric susceptibility and polarization noise was studied in glycerol below its glass transition temperature Tg. Weak FDT violations were observed after a quench from just above to just below Tg, for frequencies above the alpha peak. Violations persisted up to 10^5 times the thermal equilibration time of the configurational degrees of freedom under study, but comparable to the average relaxation time of the material. These results suggest that excess energy flows from slower to faster relaxing modes.