1,721,000 research outputs found
Inflow rate, a time-symmetric observable obeying fluctuation relations
No full textWhile entropy changes are the usual subject of fluctuation theorems, we seek fluctuation relations involving time-symmetric quantities, namely observables that do not change sign if the trajectories are observed backward in time. We find detailed and integral fluctuation relations for the (time-integrated) difference between entrance rate and escape rate in mesoscopic jump systems. Such inflow rate, which is even under time reversal, represents the discrete-state equivalent of the phase-space contraction rate. Indeed, it becomes minus the divergence of forces in the continuum limit to overdamped diffusion. This establishes a formal connection between reversible deterministic systems and irreversible stochastic ones, confirming that fluctuation theorems are largely independent of the details of the underling dynamics
Linear response in large deviations theory: a method to compute non-equilibrium distributions
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Temperature response in nonequilibrium stochastic systems
No full textThe linear response to temperature changes is derived for systems with overdamped stochastic dynamics. Holding both in transient and steady-state conditions, the results allow to compute nonequilibrium thermal susceptibilities from unperturbed correlation functions. These correlations contain a novel form of entropy flow due to temperature unbalances, next to the standard entropy flow of stochastic energetics and to complementary time-symmetric dynamical aspects. Our derivation hinges on a time rescaling, which is a key procedure for comparing apparently incommensurable path weights. An interesting notion of thermal time emerges from this approach. Copyright (C) EPLA, 201
Local detailed balance across scales: From diffusions to jump processes and beyond
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Thermokinetic relations
Full text linkThermokinetic relations bound thermodynamic quantities, such as entropy production of a physical system over a certain time interval, with statistics of kinetic (or dynamical) observables, such as mean total variation of the observable over the time interval. We introduce a thermokinetic relation to bound the entropy production or the nonadiabatic (or excess) entropy production for overdamped Markov jump processes, possibly with time-varying rates and nonstationary distributions. For stationary cases, this bound is akin to a thermodynamic uncertainty relation, only involving absolute fluctuations rather than the mean square, thereby offering a better lower bound far from equilibrium. For nonstationary cases, this bound generalizes (classical) speed limits, where the kinetic term is not necessarily the activity (number of jumps) but any trajectory observable of interest. As a consequence, in the task of driving a system from a given probability distribution to another, we find a tradeof..
Bridging Freidlin-Wentzell large deviations theory and stochastic thermodynamics
No full textFor overdamped Langevin systems subjected to weak thermal noise and nonconservative forces, we establish a connection between Freidlin-Wentzell large deviations theory and stochastic thermodynamics. First, we derive a series expansion of the quasipotential around the detailed-balance solution, that is, the system's free energy, and identify the conditions for the linear response regime to hold, even far from equilibrium. Second, we prove that the escape rate from dissipative fixed points of the macroscopic dynamics is bounded by the entropy production of trajectories that relax into and escape from the attractors. These results provide the foundation to study the nonequilibrium thermodynamics of dissipative metastable states
Energy repartition for a harmonic chain with local reservoirs
No full textWe exactly analyze the vibrational properties of a chain of harmonic oscillators in contact with local Langevin heat baths. Nonequilibrium steady-state fluctuations are found to be described by a set of mode temperatures, independent of the strengths of both the harmonic interaction and the viscous damping. Energy is equally distributed between the conjugate variables of a given mode but differently among different modes, in a manner which depends exclusively on the bath temperatures and on the boundary conditions. We outline how bath- temperature profiles can be designed to enhance or reduce fluctuations at specific frequencies in the power spectrum of the chain length
Thermal response of nonequilibrium RC circuits
No full textWe analyze experimental data obtained from an electrical circuit having components at different temperatures, showing how to predict its response to temperature variations. This illustrates in detail how to utilize a recent linear response theory for nonequilibrium overdamped stochastic systems. To validate these results, we introduce a reweighting procedure that mimics the actual realization of the perturbation and allows extracting the susceptibility of the system from steady-state data. This procedure is closely related to other fluctuation-response relations based on the knowledge of the steady-state probability distribution. As an example, we show that the nonequilibrium heat capacity in general does not correspond to the correlation between the energy of the system and the heat flowing into it. Rather, also nondissipative aspects are relevant in the nonequilibrium fluctuation-response relations
Tight uncertainty relations for cycle currents
Full text linkSeveral recent inequalities bound the precision of a current - counting net
number of transitions in a system - by a thermodynamic measure of dissipation.
However, while currents may be defined locally, dissipation is a global
property. Inspired by the fact that ever since Carnot cycles are the unit
elements of thermodynamic processes, we prove similar bounds tailored to cycle
currents - counting net cycle completions - in terms of their conjugate
affinities. We show that these inequalities are stricter than previous ones,
even far from equilibrium, and that they allow to tighten those on transition
currents. We illustrate our results with a simple model and discuss some
technical and conceptual issues related to shifting attention from transition
to cycle observables.Comment: 5 pages, 3 figure
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