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Müller-Hermes, Alexander, Daniel Stilck França et Michael M. Wolf. « Entropy production of doubly stochastic quantum channels ». Journal of Mathematical Physics 57, no 2 (février 2016) : 022203. http://dx.doi.org/10.1063/1.4941136.
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SRIVASTAVA, Y. N., G. VITIELLO et A. WIDOM. « QUANTUM MEASUREMENTS, INFORMATION AND ENTROPY PRODUCTION ». International Journal of Modern Physics B 13, no 28 (10 novembre 1999) : 3369–82. http://dx.doi.org/10.1142/s0217979299003076.
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In order to understand the Landau–Lifshitz conjecture on the relationship between quantum measurements and the thermodynamic second law, we discuss the notion of "diabatic" and "adiabatic" forces exerted by the quantum object on the classical measurement apparatus. The notion of heat and work in measurements is made manifest in this approach and the relationship between information entropy and thermodynamic entropy is explored.
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Hossein-Nejad, Hoda, Edward J. O’Reilly et Alexandra Olaya-Castro. « Work, heat and entropy production in bipartite quantum systems ». New Journal of Physics 17, no 7 (16 juillet 2015) : 075014. http://dx.doi.org/10.1088/1367-2630/17/7/075014.
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Schmidt, Heinz-Jürgen, Jürgen Schnack et Jochen Gemmer. « Stochastic thermodynamics of a finite quantum system coupled to a heat bath ». Zeitschrift für Naturforschung A 76, no 8 (21 juin 2021) : 731–45. http://dx.doi.org/10.1515/zna-2021-0095.
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Abstract We consider a situation where an N-level system (NLS) is coupled to a heat bath without being necessarily thermalized. For this situation, we derive general Jarzynski-type equations and conclude that heat and entropy is flowing from the hot bath to the cold NLS and, vice versa, from the hot NLS to the cold bath. The Clausius relation between increase of entropy and transfer of heat divided by a suitable temperature assumes the form of two inequalities which have already been considered in the literature. Our approach is illustrated by an analytical example.
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DE ROECK, WOJCIECH, et CHRISTIAN MAES. « STEADY STATE FLUCTUATIONS OF THE DISSIPATED HEAT FOR A QUANTUM STOCHASTIC MODEL ». Reviews in Mathematical Physics 18, no 06 (juillet 2006) : 619–53. http://dx.doi.org/10.1142/s0129055x06002747.
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We introduce a quantum stochastic dynamics for heat conduction. A multi-level subsystem is coupled to reservoirs at different temperatures. Energy quanta are detected in the reservoirs allowing the study of steady state fluctuations of the entropy dissipation. Our main result states a symmetry in its large deviation rate function.
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Seifert, Udo. « From Stochastic Thermodynamics to Thermodynamic Inference ». Annual Review of Condensed Matter Physics 10, no 1 (10 mars 2019) : 171–92. http://dx.doi.org/10.1146/annurev-conmatphys-031218-013554.
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For a large class of nonequilibrium systems, thermodynamic notions like work, heat, and, in particular, entropy production can be identified on the level of fluctuating dynamical trajectories. Within stochastic thermodynamics various fluctuation theorems relating these quantities have been proven. Their application to experimental systems requires that all relevant mesostates are accessible. Recent advances address the typical situation that only partial, or coarse-grained, information about a system is available. Thermodynamic inference as a general strategy uses consistency constraints derived from stochastic thermodynamics to infer otherwise hidden properties of nonequilibrium systems. An important class in this respect are active particles, for which we resolve the conflicting strategies that have been proposed to identify entropy production. As a paradigm for thermodynamic inference, the thermodynamic uncertainty relation provides a lower bound on the entropy production through measurements of the dispersion of any current in the system. Likewise, it quantifies the cost of precision for biomolecular processes. Generalizations and ramifications allow the inference of, inter alia, model-free upper bounds on the efficiency of molecular motors and of the minimal number of intermediate states in enzymatic networks.
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Bonetto, F., J. L. Lebowitz, J. Lukkarinen et S. Olla. « Heat Conduction and Entropy Production in Anharmonic Crystals with Self-Consistent Stochastic Reservoirs ». Journal of Statistical Physics 134, no 5-6 (9 décembre 2008) : 1097–119. http://dx.doi.org/10.1007/s10955-008-9657-1.
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Strasberg, Philipp. « Thermodynamics of Quantum Causal Models : An Inclusive, Hamiltonian Approach ». Quantum 4 (2 mars 2020) : 240. http://dx.doi.org/10.22331/q-2020-03-02-240.
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Operational quantum stochastic thermodynamics is a recently proposed theory to study the thermodynamics of open systems based on the rigorous notion of a quantum stochastic process or quantum causal model. In there, a stochastic trajectory is defined solely in terms of experimentally accessible measurement results, which serve as the basis to define the corresponding thermodynamic quantities. In contrast to this observer-dependent point of view, a `black box', which evolves unitarily and can simulate a quantum causal model, is constructed here. The quantum thermodynamics of this big isolated system can then be studied using widely accepted arguments from statistical mechanics. It is shown that the resulting definitions of internal energy, heat, work, and entropy have a natural extension to the trajectory level. The canonical choice of them coincides with the proclaimed definitions of operational quantum stochastic thermodynamics, thereby providing strong support in favour of that novel framework. However, a few remaining ambiguities in the definition of stochastic work and heat are also discovered and in light of these findings some other proposals are reconsidered. Finally, it is demonstrated that the first and second law hold for an even wider range of scenarios than previously thought, covering a large class of quantum causal models based solely on a single assumption about the initial system-bath state.
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Borlenghi, Simone, et Anna Delin. « Stochastic Thermodynamics of Oscillators’ Networks ». Entropy 20, no 12 (19 décembre 2018) : 992. http://dx.doi.org/10.3390/e20120992.
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We apply the stochastic thermodynamics formalism to describe the dynamics of systems of complex Langevin and Fokker-Planck equations. We provide in particular a simple and general recipe to calculate thermodynamical currents, dissipated and propagating heat for networks of nonlinear oscillators. By using the Hodge decomposition of thermodynamical forces and fluxes, we derive a formula for entropy production that generalises the notion of non-potential forces and makes transparent the breaking of detailed balance and of time reversal symmetry for states arbitrarily far from equilibrium. Our formalism is then applied to describe the off-equilibrium thermodynamics of a few examples, notably a continuum ferromagnet, a network of classical spin-oscillators and the Frenkel-Kontorova model of nano friction.
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BENJAMIN, RONALD. « STOCHASTIC ENERGETICS OF A BROWNIAN MOTOR AND REFRIGERATOR DRIVEN BY NONUNIFORM TEMPERATURE ». International Journal of Modern Physics B 28, no 08 (24 février 2014) : 1450055. http://dx.doi.org/10.1142/s0217979214500556.
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The energetics of a Brownian heat engine and heat pump driven by position dependent temperature, known as the Büttiker–Landauer heat engine and heat pump, is investigated by numerical simulations of the inertial Langevin equation. We identify parameter values for optimal performance of the heat engine and heat pump. Our results qualitatively differ from approaches based on the overdamped model. The behavior of the heat engine and heat pump, in the linear response regime is examined under finite time conditions and we find that the efficiency is lower than that of an endoreversible engine working under the same condition. Finally, we investigate the role of different potential and temperature profiles to enhance the efficiency of the system. Our simulations show that optimizing the potential and temperature profile leads only to a marginal enhancement of the system performance due to the large entropy production via the Brownian particle's kinetic energy.
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O'CONNELL, R. F. « BLACKBODY RADIATION : ROSETTA STONE OF HEAT BATH MODELS ». Fluctuation and Noise Letters 07, no 04 (décembre 2007) : L483—L490. http://dx.doi.org/10.1142/s0219477507004124.
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The radiation field can be regarded as a collection of independent harmonic oscillators and, as such, constitutes a heat bath. Moreover, the known form of its interaction with charged particles provides a "rosetta stone" for deciding on and interpreting the correct interaction for the more general case of a quantum particle in an external potential and coupled to an arbitrary heat bath. In particular, combining QED with the machinery of stochastic physics, enables the usual scope of applications to be widened. We discuss blackbody radiation effects on: the equation of motion of a radiating electron (obtaining an equation of motion which is free from runaway solutions), anomalous diffusion, the spreading of a Gaussian wave packet, and decoherence effects due to zero-point oscillations. In addition, utilizing a formula we obtained for the free energy of an oscillator in a heat bath, enables us to determine all the quantum thermodynamic functions of interest (particularly in the areas of quantum information and nanophysics where small systems are involved) and from which we obtain temperature dependent Lamb shifts, quantum effects on the entropy at low temperature and implications for Nernst's law.
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Chiarelli, Piero. « Far from Equilibrium Maximal Principle Leading to Matter Self-Organization ». JOURNAL OF ADVANCES IN CHEMISTRY 5, no 3 (2 décembre 2009) : 753–83. http://dx.doi.org/10.24297/jac.v5i3.2664.
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In this work an extremal principle driving the far from equilibrium evolution of a system of structureless particles is derived by using the stochastic quantum hydrodynamic analogy. For a classical phase (i.e., the quantum correlations decay on a distance smaller than the mean inter-molecular distance) the far from equilibrium kinetic equation can be cast in the form of a Fokker-Plank equation whose phase space velocity vector maximizes the dissipation of the energy-type function, named here, stochastic free energy.Near equilibrium the maximum stochastic free energy dissipation (SFED) is shown to be compatible with the Prigogine’s principle of minimum entropy production. Moreover, in quasi-isothermal far from equilibrium states, the theory shows that, in the case of elastic molecular collisions and in absence of chemical reactions, the maximum SFED reduces to the maximum free energy dissipation.When chemical reactions or relevant thermal gradients are present, the theory highlights that the Sawada enunciation of maximum free energy dissipation can be violated.The proposed model depicts the Prigogine’s principle of minimum entropy production near-equilibrium and the far from equilibrium Sawada’s principle of maximum energy dissipation as two complementary principia of a unique theory where the latter one is a particular case of the more general one of maximum stochastic free energy dissipation.Following the tendency to reach the highest rate of SFED, a system relaxing to equilibrium goes through states with higher order so that the matter self-organization becomes possible.
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HE, JI-ZHOU, JIAN-HUI WANG et XIN-FA DENG. « THE INFLUENCE OF HEAT LEAKAGE AND INTERNAL IRREVERSIBILITY ON THE PERFORMANCE OF A QUANTUM SPIN REFRIGERATION CYCLE ». International Journal of Modern Physics B 24, no 23 (20 septembre 2010) : 4595–610. http://dx.doi.org/10.1142/s0217979210056591.
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The cycle model established here, for which the heat leakage and internal irreversibility are considered, consists of two irreversible non-isentropic adiabatic and two isomagnetic field processes. The working substance is composed of many non-interacting spin systems. Based on quantum master equation of an open system in the Heisenberg picture and semi-group approach, the general performance analysis of quantum refrigeration cycle is performed. Expressions for several important performance parameters, such as the cooling rate, coefficient of performance, rate of entropy production and power input, are derived. By using numerical calculations, the cooling rate as a natural optimization goal for a refrigerator is optimized with respect to external magnetic field. The characteristic curves of the cooling rate, rate of entropy production and power input subject to coefficient of performance are plotted. The optimal regions of the cooling rate, coefficient of the performance (COP) and temperatures of the working substance, are determined.
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Fernández, J. J. « Optimization of energy production in two-qubit heat engines using the ecological function ». Quantum Science and Technology 7, no 3 (19 avril 2022) : 035002. http://dx.doi.org/10.1088/2058-9565/ac635a.
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Abstract We study the ecological regime of quantum heat engines where the heat transfer between the environment and the engine is mediated with two qubits that act as energy filters and allow the conversion of heat into work. Using quantum thermodynamics, the theory of open quantum system and the fundamentals of finite-time thermodynamics we obtain the output power, the ecological function and the entropy production of the engine. Then, we optimize the functioning to the ecological function to find the range of efficiencies for which the system works optimally under the ecological criterium. We find that (i) the maximum value of the ecological function depends on the thermal copulings and the energies of the qubits that define the engine. (ii) We can define an ecological working region where the engine works producing a power that is similar to the maximum power but where it rejects much less heat to the environment. (iii) That the range of efficiencies defining the ecological region depends on the parameters defining the engine.(iv) An optimal working region where both the power and the ecological function are big is defined for each machine.
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Peterson, J. P. S., R. S. Sarthour, A. M. Souza, I. S. Oliveira, J. Goold, K. Modi, D. O. Soares-Pinto et L. C. Céleri. « Experimental demonstration of information to energy conversion in a quantum system at the Landauer limit ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 472, no 2188 (avril 2016) : 20150813. http://dx.doi.org/10.1098/rspa.2015.0813.
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Landauer’s principle sets fundamental thermodynamical constraints for classical and quantum information processing, thus affecting not only various branches of physics, but also of computer science and engineering. Despite its importance, this principle was only recently experimentally considered for classical systems. Here we employ a nuclear magnetic resonance set-up to experimentally address the information to energy conversion in a quantum system. Specifically, we consider a three nuclear spins S = 1 2 (qubits) molecule—the system, the reservoir and the ancilla—to measure the heat dissipated during the implementation of a global system–reservoir unitary interaction that changes the information content of the system. By employing an interferometric technique, we were able to reconstruct the heat distribution associated with the unitary interaction. Then, through quantum state tomography, we measured the relative change in the entropy of the system. In this way, we were able to verify that an operation that changes the information content of the system must necessarily generate heat in the reservoir, exactly as predicted by Landauer’s principle. The scheme presented here allows for the detailed study of irreversible entropy production in quantum information processors.
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Genthon, Arthur, Reinaldo García-García et David Lacoste. « Branching processes with resetting as a model for cell division ». Journal of Physics A : Mathematical and Theoretical 55, no 7 (26 janvier 2022) : 074001. http://dx.doi.org/10.1088/1751-8121/ac491a.
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Abstract We study the stochastic thermodynamics of cell growth and division using a theoretical framework based on branching processes with resetting. Cell division may be split into two sub-processes: branching, by which a given cell gives birth to an identical copy of itself, and resetting, by which some properties of the daughter cells (such as their size or age) are reset to new values following division. We derive the first and second laws of stochastic thermodynamics for this process, and identify separate contributions due to branching and resetting. We apply our framework to well-known models of cell size control, such as the sizer, the timer, and the adder. We show that the entropy production of resetting is negative and that of branching is positive for these models in the regime of exponential growth of the colony. This property suggests an analogy between our model for cell growth and division and heat engines, and the introduction of a thermodynamic efficiency, which quantifies the conversion of one form of entropy production to another.
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Dann, Roie, Ronnie Kosloff et Peter Salamon. « Quantum Finite-Time Thermodynamics : Insight from a Single Qubit Engine ». Entropy 22, no 11 (4 novembre 2020) : 1255. http://dx.doi.org/10.3390/e22111255.
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Incorporating time into thermodynamics allows for addressing the tradeoff between efficiency and power. A qubit engine serves as a toy model in order to study this tradeoff from first principles, based on the quantum theory of open systems. We study the quantum origin of irreversibility, originating from heat transport, quantum friction, and thermalization in the presence of external driving. We construct various finite-time engine cycles that are based on the Otto and Carnot templates. Our analysis highlights the role of coherence and the quantum origin of entropy production.
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Vanchurin, Vitaly. « Towards a Theory of Quantum Gravity from Neural Networks ». Entropy 24, no 1 (21 décembre 2021) : 7. http://dx.doi.org/10.3390/e24010007.
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Neural network is a dynamical system described by two different types of degrees of freedom: fast-changing non-trainable variables (e.g., state of neurons) and slow-changing trainable variables (e.g., weights and biases). We show that the non-equilibrium dynamics of trainable variables can be described by the Madelung equations, if the number of neurons is fixed, and by the Schrodinger equation, if the learning system is capable of adjusting its own parameters such as the number of neurons, step size and mini-batch size. We argue that the Lorentz symmetries and curved space-time can emerge from the interplay between stochastic entropy production and entropy destruction due to learning. We show that the non-equilibrium dynamics of non-trainable variables can be described by the geodesic equation (in the emergent space-time) for localized states of neurons, and by the Einstein equations (with cosmological constant) for the entire network. We conclude that the quantum description of trainable variables and the gravitational description of non-trainable variables are dual in the sense that they provide alternative macroscopic descriptions of the same learning system, defined microscopically as a neural network.
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Loos, Sarah A. M., Simon Hermann et Sabine H. L. Klapp. « Medium Entropy Reduction and Instability in Stochastic Systems with Distributed Delay ». Entropy 23, no 6 (31 mai 2021) : 696. http://dx.doi.org/10.3390/e23060696.
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Many natural and artificial systems are subject to some sort of delay, which can be in the form of a single discrete delay or distributed over a range of times. Here, we discuss the impact of this distribution on (thermo-)dynamical properties of time-delayed stochastic systems. To this end, we study a simple classical model with white and colored noise, and focus on the class of Gamma-distributed delays which includes a variety of distinct delay distributions typical for feedback experiments and biological systems. A physical application is a colloid subject to time-delayed feedback control, which is, in principle, experimentally realizable by co-moving optical traps. We uncover several unexpected phenomena in regard to the system’s linear stability and its thermodynamic properties. First, increasing the mean delay time can destabilize or stabilize the process, depending on the distribution of the delay. Second, for all considered distributions, the heat dissipated by the controlled system (e.g., the colloidal particle) can become negative, which implies that the delay force extracts energy and entropy of the bath. As we show here, this refrigerating effect is particularly pronounced for exponential delay. For a specific non-reciprocal realization of a control device, we find that the entropic costs, measured by the total entropy production of the system plus controller, are the lowest for exponential delay. The exponential delay further yields the largest stable parameter regions. In this sense, exponential delay represents the most effective and robust type of delayed feedback.
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Braak, D., et J. Mannhart. « Fermi’s Golden Rule and the Second Law of Thermodynamics ». Foundations of Physics 50, no 11 (18 septembre 2020) : 1509–40. http://dx.doi.org/10.1007/s10701-020-00380-2.
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AbstractWe present a Gedankenexperiment that leads to a violation of detailed balance if quantum mechanical transition probabilities are treated in the usual way by applying Fermi’s “golden rule”. This Gedankenexperiment introduces a collection of two-level systems that absorb and emit radiation randomly through non-reciprocal coupling to a waveguide, as realized in specific chiral quantum optical systems. The non-reciprocal coupling is modeled by a hermitean Hamiltonian and is compatible with the time-reversal invariance of unitary quantum dynamics. Surprisingly, the combination of non-reciprocity with probabilistic radiation processes entails negative entropy production. Although the considered system appears to fulfill all conditions for Markovian stochastic dynamics, such a dynamics violates the Clausius inequality, a formulation of the second law of thermodynamics. Several implications concerning the interpretation of the quantum mechanical formalism are discussed.
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Oh, Sangchul, Jung Jun Park et Hyunchul Nha. « Quantum Photovoltaic Cells Driven by Photon Pulses ». Entropy 22, no 6 (20 juin 2020) : 693. http://dx.doi.org/10.3390/e22060693.
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We investigate the quantum thermodynamics of two quantum systems, a two-level system and a four-level quantum photocell, each driven by photon pulses as a quantum heat engine. We set these systems to be in thermal contact only with a cold reservoir while the heat (energy) source, conventionally given from a hot thermal reservoir, is supplied by a sequence of photon pulses. The dynamics of each system is governed by a coherent interaction due to photon pulses in terms of the Jaynes-Cummings Hamiltonian together with the system-bath interaction described by the Lindblad master equation. We calculate the thermodynamic quantities for the two-level system and the quantum photocell including the change in system energy, the power delivered by photon pulses, the power output to an external load, the heat dissipated to a cold bath, and the entropy production. We thereby demonstrate how a quantum photocell in the cold bath can operate as a continuum quantum heat engine with a sequence of photon pulses continuously applied. We specifically introduce the power efficiency of the quantum photocell in terms of the ratio of output power delivered to an external load with current and voltage to the input power delivered by the photon pulse. Our study indicates a possibility that a quantum system driven by external fields can act as an efficient quantum heat engine under non-equilibrium thermodynamics.
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Abiuso, Paolo, Harry J. D. Miller, Martí Perarnau-Llobet et Matteo Scandi. « Geometric Optimisation of Quantum Thermodynamic Processes ». Entropy 22, no 10 (24 septembre 2020) : 1076. http://dx.doi.org/10.3390/e22101076.
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Differential geometry offers a powerful framework for optimising and characterising finite-time thermodynamic processes, both classical and quantum. Here, we start by a pedagogical introduction to the notion of thermodynamic length. We review and connect different frameworks where it emerges in the quantum regime: adiabatically driven closed systems, time-dependent Lindblad master equations, and discrete processes. A geometric lower bound on entropy production in finite-time is then presented, which represents a quantum generalisation of the original classical bound. Following this, we review and develop some general principles for the optimisation of thermodynamic processes in the linear-response regime. These include constant speed of control variation according to the thermodynamic metric, absence of quantum coherence, and optimality of small cycles around the point of maximal ratio between heat capacity and relaxation time for Carnot engines.
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Bhattacharyya, Swarnapratim, Maria Haiduc, Alina Tania Neagu et Elena Firu. « Multifractal Analysis of Charged Particle Multiplicity Distribution in the Framework of Renyi Entropy ». Advances in High Energy Physics 2018 (26 juin 2018) : 1–15. http://dx.doi.org/10.1155/2018/6384357.
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A study of multifractality and multifractal specific heat has been carried out for the produced shower particles in nuclear emulsion detector for 16O-AgBr, 28Si-AgBr, and 32S-AgBr interactions at 4.5AGeV/c in the framework of Renyi entropy. Experimental results have been compared with the prediction of Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) model. Our analysis reveals the presence of multifractality in the multiparticle production process in high energy nucleus-nucleus interactions. Degree of multifractality is found to be higher for the experimental data and it increases with the increase of projectile mass. The investigation of quark-hadron phase transition in the multiparticle production in 16O-AgBr, 28Si-AgBr, and 32S-AgBr interactions at 4.5 AGeV/c in the framework of Ginzburg-Landau theory from the concept of multifractality has also been presented. Evidence of constant multifractal specific heat has been obtained for both experimental and UrQMD simulated data.
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Mintchev, Mihail. « Quantum states from mixtures of equilibrium distributions ». Journal of Statistical Mechanics : Theory and Experiment 2022, no 4 (1 avril 2022) : 043103. http://dx.doi.org/10.1088/1742-5468/ac6252.
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Abstract We construct and explore a family of states for quantum systems in contact with two or more heath reservoirs. The reservoirs are described by equilibrium distributions. The interaction of each reservoir with the bulk of the system is encoded in a probability, which characterises the particle exchange among them and depends in general on the particle momentum. The convex combination of the reservoir distributions, weighted with the aforementioned probabilities, defines a new distribution. We establish the existence of an emission–absorption regime in which the new distribution generates a non-equilibrium quantum state. We develop a systematic field theory framework for constructing this state and illustrate its physical properties on a simple model. In this context we derive the particle current full counting statistics, the heat current and the Lorenz number. The entropy production and the relative quantum fluctuations are also determined.
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Mintchev, Mihail. « Quantum states from mixtures of equilibrium distributions ». Journal of Statistical Mechanics : Theory and Experiment 2022, no 4 (1 avril 2022) : 043103. http://dx.doi.org/10.1088/1742-5468/ac6252.
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Abstract We construct and explore a family of states for quantum systems in contact with two or more heath reservoirs. The reservoirs are described by equilibrium distributions. The interaction of each reservoir with the bulk of the system is encoded in a probability, which characterises the particle exchange among them and depends in general on the particle momentum. The convex combination of the reservoir distributions, weighted with the aforementioned probabilities, defines a new distribution. We establish the existence of an emission–absorption regime in which the new distribution generates a non-equilibrium quantum state. We develop a systematic field theory framework for constructing this state and illustrate its physical properties on a simple model. In this context we derive the particle current full counting statistics, the heat current and the Lorenz number. The entropy production and the relative quantum fluctuations are also determined.
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Majumdar, Rita, Arnab Saha et Rahul Marathe. « Exactly solvable model of a passive Brownian heat engine and its comparison with active engines ». Journal of Statistical Mechanics : Theory and Experiment 2022, no 7 (1 juillet 2022) : 073206. http://dx.doi.org/10.1088/1742-5468/ac7e3d.
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Abstract We perform an extensive analysis of passive as well as active micro-heat engines with different single-particle stochastic models. Using stochastic thermodynamics we calculate the thermodynamic work, heat, entropy production and efficiency of passive and active Brownian heat engines analytically, as well as numerically, and compare them. We run the heat engines with a protocol for which the average thermodynamic quantities are calculated exactly for an arbitrary cycle time. We also discuss the group of protocols for which exact non-quasistatic calculations can be done, completely in the passive engine case and partially in the active engines. We obtain detailed thermodynamics of non-quasistatic (i.e. powerful) single-particle micro heat engines. The quasistatic (i.e. zero power) limit of the results is obtained by taking a long (infinite) cycle time. We also study the distributions of position of the confined particle in both passive and active engines. We compare their characteristics in terms of the parameter that measures the competition between the active persistence in the particle position (due to active noises) and the harmonic confinement. We also calculate excess kurtosis that measures the non-Gaussianity of these distributions. Our analysis shows that the efficiency of such thermal machines can be enhanced or reduced depending on the activity present in the model.
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Pal, P. S., Arnab Saha et A. M. Jayannavar. « Operational characteristics of single-particle heat engines and refrigerators with time-asymmetric protocol ». International Journal of Modern Physics B 30, no 31 (5 décembre 2016) : 1650219. http://dx.doi.org/10.1142/s0217979216502192.
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We have studied the single-particle heat engine and refrigerator driven by time-asymmetric protocol of finite duration. Our system consists of a particle in a harmonic trap with time-periodic strength that drives the particle cyclically between two baths. Each cycle consists of two isothermal steps at different temperatures and two adiabatic steps connecting them. The system works in irreversible mode of operation even in the quasistatic regime. This is indicated by finite entropy production even in the large cycle time limit. Consequently, Carnot efficiency for heat engine or Carnot coefficient of performance (COP) for refrigerators is not achievable. We further analyzed the phase diagram of heat engines and refrigerators. They are sensitive to time-asymmetry of the protocol. Phase diagram shows several interesting features, often counterintuitive. The distribution of stochastic efficiency and COP is broad and exhibits power-law tails.
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Nelson, Elliot, et C. Jess Riedel. « Classical entanglement structure in the wavefunction of inflationary fluctuations ». International Journal of Modern Physics D 26, no 12 (octobre 2017) : 1743006. http://dx.doi.org/10.1142/s0218271817430064.
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We argue that preferred classical variables emerge from the entanglement structure of a pure quantum state in the form of redundant records: information shared between many subsystems. Focusing on the early universe, we ask how classical metric perturbations emerge from vacuum fluctuations in an inflationary background. We show that the squeezing of the quantum state for super-horizon modes, along with minimal gravitational interactions, leads to decoherence and to an exponential number of records of metric fluctuations on very large scales, [Formula: see text], where [Formula: see text] is the amplitude of metric fluctuations. This determines a preferred decomposition of the inflationary wavefunction into orthogonal “branches” corresponding to classical metric perturbations, which defines an inflationary entropy production rate and accounts for the emergence of stochastic, inhomogeneous spacetime geometry.
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Aghion, Erez, et Jason R. Green. « Thermodynamic speed limits for mechanical work ». Journal of Physics A : Mathematical and Theoretical 56, no 5 (3 février 2023) : 05LT01. http://dx.doi.org/10.1088/1751-8121/acb5d6.
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Abstract Thermodynamic speed limits are a set of classical uncertainty relations that, so far, place global bounds on the stochastic dissipation of energy as heat and the production of entropy. Here, instead of constraints on these thermodynamic costs, we derive integral speed limits that are upper and lower bounds on a thermodynamic benefit—the minimum time for an amount of mechanical work to be done on or by a system. In the short time limit, we show how this extrinsic timescale relates to an intrinsic timescale for work, recovering the intrinsic timescales in differential speed limits from these integral speed limits and turning the first law of stochastic thermodynamics into a first law of speeds. As physical examples, we consider the work done by a flashing Brownian ratchet and the work done on a particle in a potential well subject to external driving.
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Ostoja-Starzewski, M., et A. Malyarenko. « Continuum mechanics beyond the second law of thermodynamics ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 470, no 2171 (8 novembre 2014) : 20140531. http://dx.doi.org/10.1098/rspa.2014.0531.
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The results established in contemporary statistical physics indicating that, on very small space and time scales, the entropy production rate may be negative, motivate a generalization of continuum mechanics. On account of the fluctuation theorem, it is recognized that the evolution of entropy at a material point is stochastically (not deterministically) conditioned by the past history, with an increasing trend of average entropy production. Hence, the axiom of Clausius–Duhem inequality is replaced by a submartingale model, which, by the Doob decomposition theorem, allows classification of thermomechanical processes into four types depending on whether they are conservative or not and/or conventional continuum mechanical or not. Stochastic generalizations of thermomechanics are given in the vein of either thermodynamic orthogonality or primitive thermodynamics, with explicit models formulated for Newtonian fluids with, respectively, parabolic or hyperbolic heat conduction. Several random field models of the martingale component, possibly including spatial fractal and Hurst effects, are proposed. The violations of the second law are relevant in those situations in continuum mechanics where very small spatial and temporal scales are involved. As an example, we study an acceleration wavefront of nanoscale thickness which randomly encounters regions in the medium characterized by a negative viscosity coefficient.
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Vanchurin, Vitaly. « The World as a Neural Network ». Entropy 22, no 11 (26 octobre 2020) : 1210. http://dx.doi.org/10.3390/e22111210.
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We discuss a possibility that the entire universe on its most fundamental level is a neural network. We identify two different types of dynamical degrees of freedom: “trainable” variables (e.g., bias vector or weight matrix) and “hidden” variables (e.g., state vector of neurons). We first consider stochastic evolution of the trainable variables to argue that near equilibrium their dynamics is well approximated by Madelung equations (with free energy representing the phase) and further away from the equilibrium by Hamilton–Jacobi equations (with free energy representing the Hamilton’s principal function). This shows that the trainable variables can indeed exhibit classical and quantum behaviors with the state vector of neurons representing the hidden variables. We then study stochastic evolution of the hidden variables by considering D non-interacting subsystems with average state vectors, x¯1, …, x¯D and an overall average state vector x¯0. In the limit when the weight matrix is a permutation matrix, the dynamics of x¯μ can be described in terms of relativistic strings in an emergent D+1 dimensional Minkowski space-time. If the subsystems are minimally interacting, with interactions that are described by a metric tensor, and then the emergent space-time becomes curved. We argue that the entropy production in such a system is a local function of the metric tensor which should be determined by the symmetries of the Onsager tensor. It turns out that a very simple and highly symmetric Onsager tensor leads to the entropy production described by the Einstein–Hilbert term. This shows that the learning dynamics of a neural network can indeed exhibit approximate behaviors that were described by both quantum mechanics and general relativity. We also discuss a possibility that the two descriptions are holographic duals of each other.
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Agrebi, Senda, Louis Dreßler, Hendrik Nicolai, Florian Ries, Kaushal Nishad et Amsini Sadiki. « Analysis of Local Exergy Losses in Combustion Systems Using a Hybrid Filtered Eulerian Stochastic Field Coupled with Detailed Chemistry Tabulation : Cases of Flames D and E ». Energies 14, no 19 (3 octobre 2021) : 6315. http://dx.doi.org/10.3390/en14196315.
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A second law analysis in combustion systems is performed along with an exergy loss study by quantifying the entropy generation sources using, for the first time, three different approaches: a classical-thermodynamics-based approach, a novel turbulence-based method and a look-up-table-based approach, respectively. The numerical computation is based on a hybrid filtered Eulerian stochastic field (ESF) method coupled with tabulated detailed chemistry according to a Famelet-Generated Manifold (FGM)-based combustion model. In this work, the capability of the three approaches to capture the effect of the Re number on local exergy losses is especially appraised. For this purpose, Sandia flames D and E are selected as application cases. First, the validation of the computed flow and scalar fields is achieved by comparison to available experimental data. For both flames, the flow field results for eight stochastic fields and the associated scalar fields show an excellent agreement. The ESF method reproduces all major features of the flames at a lower numerical cost. Next, the second law analysis carried out with the different approaches for the entropy generation computation provides comparable quantitative results. Using flame D as a reference, for which some results with the thermodynamic-based approach exist in the literature, it turns out that, among the sources of exergy loss, the heat transfer and the chemical reaction emerge notably as the main culprits for entropy production, causing 50% and 35% of it, respectively. This fact-finding increases in Sandia flame E, which features a high Re number compared to Sandia flame D. The computational cost is less once the entropy generation analysis is carried out by using the Large Eddy Simulation (LES) hybrid ESF/FGM approach together with the look-up-table-based or turbulence-based approach.
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Castorina, Paolo, Alfredo Iorio et Helmut Satz. « Hunting Quantum Gravity with Analogs : The Case of High-Energy Particle Physics ». Universe 8, no 9 (13 septembre 2022) : 482. http://dx.doi.org/10.3390/universe8090482.
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In this review, we collect, for the first time, old and new research results, and present future perspectives on how hadron production, in high-energy scattering processes, can experimentally probe fundamental questions of quantum gravity. The key observations that ignited the link between the two arenas are the so-called “color-event horizon” of quantum chromodynamics, and the (de)accelerations involved in such scattering processes. Both phenomena point to the Unruh (and related Hawking)-type effects. After the first pioneering investigations, such research studies continued, including studies of the horizon entropy and other “black-hole thermodynamical” behaviors, which incidentally are also part of the frontier of the analog gravity research itself. It has been stressed that the trait d’union between the two phenomenologies is that in both hadron physics and black hole physics, “thermal” behaviors are more easily understood, not as due to real thermalization processes (sometimes just impossible, given the small number of particles involved), but rather to a stochastic/quantum entanglement nature of such temperatures. Finally, other aspects, such as the self-critical organizations of hadronic matter and of black holes, have been recently investigated. The results of those investigations are also summarized and commented upon here. As a general remark, this research line shows that we can probe quantum gravity theoretical constructions with analog systems that are not confined to only the condensed matter arena.
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Brandner, Kay. « Coherent Transport in Periodically Driven Mesoscopic Conductors : From Scattering Amplitudes to Quantum Thermodynamics ». Zeitschrift für Naturforschung A 75, no 5 (26 mai 2020) : 483–500. http://dx.doi.org/10.1515/zna-2020-0056.
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AbstractScattering theory is a standard tool for the description of transport phenomena in mesoscopic systems. Here, we provide a detailed derivation of this method for nano-scale conductors that are driven by oscillating electric or magnetic fields. Our approach is based on an extension of the conventional Lippmann–Schwinger formalism to systems with a periodically time-dependent Hamiltonian. As a key result, we obtain a systematic perturbation scheme for the Floquet scattering amplitudes that describes the transition of a transport carrier through a periodically driven sample. Within a general multi-terminal setup, we derive microscopic expressions for the mean values and time-integrated correlation functions, or zero-frequency noise, of matter and energy currents, thus recovering the results of earlier studies in a unifying framework. We show that this framework is inherently consistent with the first and the second law of thermodynamics and prove that the mean rate of entropy production vanishes only if all currents in the system are zero. As an application, we derive a generalized Green–Kubo relation, which makes it possible to express the response of any mean currents to small variations of temperature and chemical potential gradients in terms of time integrated correlation functions between properly chosen currents. Finally, we discuss potential topics for future studies and further reaching applications of the Floquet scattering approach to quantum transport in stochastic and quantum thermodynamics.
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Blokhin, A. V., et Ya N. Yurkshtovich. « Thermodynamic properties of L-menthol in crystalline and gaseous states ». Fine Chemical Technologies 15, no 1 (21 mars 2020) : 28–36. http://dx.doi.org/10.32362/2410-6593-2020-15-1-28-36.
Texte intégralRésumé :
Objectives. Menthol causes a cooling sensation and reduces the nerve activity when it is applied locally, ingested, or inhaled. This feature explains its extensive use as both an aromatizer and a flavoring agent in food manufacturing, tobacco industry, cosmetics production, as well as a mild anesthetic and antiseptic in dentistry. This work aimed to perform a comprehensive thermodynamic study of L-menthol in both crystalline and gaseous states.Methods. To determine the combustion energy of L-menthol in the crystalline state, combustion bomb calorimetry was used. The temperature dependence of L-menthol’s heat capacity in the range of 5–370 K and the melting (fusion) parameters were determined using adiabatic calorimetry. Quantum chemical calculations were performed on a standalone virtual machine in the Google Cloud Platform using an eight-core Intel Xeon Scalable Processor (Skylake) with a 2.0 GHz (up to 2.7 GHz at peak load) clock frequency and 8 GB RAM.Results. The energy and enthalpy of L-menthol combustion in the crystalline state were determined, and the standard enthalpy of L-menthol formation in the gaseous state was calculated using the standard enthalpy of sublimation. The standard thermodynamic functions (reduced enthalpy, entropy, and reduced Gibbs energy) of L-menthol in both crystalline and liquid states were obtained based on the smoothed values of heat capacity and melting parameters. The group of isodesmic reactions for the ab initio calculation of the enthalpy of formation for gaseous L-menthol was substantiated. Electronic energy and frequencies of normal modes of the molecules involved in these reactions were calculated using the Gaussian 4 composite quantum chemical method. Further, the sublimation enthalpy of L-menthol was calculated using the extended Politzer equation according to the electrostatic potential model.Conclusions. The first comprehensive thermodynamic study of L-menthol in various states of aggregation was performed, and the values calculated using semiempirical methods were consistent with the experimental values within error limits, which confirms the reliability of the results.
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Ahmadi, B., S. Salimi et A. S. Khorashad. « Irreversible work and Maxwell demon in terms of quantum thermodynamic force ». Scientific Reports 11, no 1 (27 janvier 2021). http://dx.doi.org/10.1038/s41598-021-81737-z.
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AbstractThe second law of classical equilibrium thermodynamics, based on the positivity of entropy production, asserts that any process occurs only in a direction that some information may be lost (flow out of the system) due to the irreversibility inside the system. However, any thermodynamic system can exhibit fluctuations in which negative entropy production may be observed. In particular, in stochastic quantum processes due to quantum correlations and also memory effects we may see the reversal energy flow (heat flow from the cold system to the hot system) and the backflow of information into the system that leads to the negativity of the entropy production which is an apparent violation of the Second Law. In order to resolve this apparent violation, we will try to properly extend the Second Law to quantum processes by incorporating information explicitly into the Second Law. We will also provide a thermodynamic operational meaning for the flow and backflow of information. Finally, it is shown that negative and positive entropy production can be described by a quantum thermodynamic force.
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Guéry-Odelin, David, Chris Jarzynski, Carlos A. Plata, Antonio Prados et Emmanuel Trizac. « Driving rapidly while remaining in control : classical shortcuts from Hamiltonian to stochastic dynamics ». Reports on Progress in Physics, 19 décembre 2022. http://dx.doi.org/10.1088/1361-6633/acacad.
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Abstract Stochastic thermodynamics lays down a broad framework to revisit the venerable concepts of heat, work and entropy production for individual stochastic trajectories of mesoscopic systems. Remarkably, this approach, relying on stochastic equations of motion, introduces time into the description of thermodynamic processes---which opens the way to fine control them. As a result, the field of finite-time thermodynamics of mesoscopic systems has blossomed. In this article, after introducing a few concepts of control for isolated mechanical systems evolving according to deterministic equations of motion, we review the different strategies that have been developed to realize finite-time state-to-state transformations in both over and underdamped regimes, by the proper design of time-dependent control parameters/driving. The systems under study are stochastic, epitomized by a Brownian object immersed in a fluid; they are thus strongly coupled to their environment playing the role of a reservoir. Interestingly, a few of those methods (inverse engineering, counterdiabatic driving, fast-forward) are directly inspired by their counterpart in quantum control. The review also analyzes the control through reservoir engineering. Besides the reachability of a given target state from a known initial state, the question of the optimal path is discussed. Optimality is here defined with respect to a cost function, a subject intimately related to the field of information thermodynamics and the question of speed limit. Another natural extension discussed deals with the connection between arbitrary states or non-equilibrium steady states. This field of control in stochastic thermodynamics enjoys a wealth of applications, ranging from optimal mesoscopic heat engines to population control in biological systems.
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Matos, Daniel, Lev N. Kantorovich et Ian J. Ford. « Stochastic entropy production for continuous measurements of an open quantum system ». Journal of Physics Communications, 29 novembre 2022. http://dx.doi.org/10.1088/2399-6528/aca742.
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Abstract We investigate the total stochastic entropy production of a two-level bosonic open quantum system under protocols of time dependent coupling to a harmonic environment. These processes are intended to represent the measurement of a system observable, and consequent selection of an eigenstate, whilst the system is also subjected to thermalising environmental noise. The entropy production depends on the evolution of the system variables and their probability density function, and is expressed through system and environmental contributions. The continuous stochastic dynamics of the open system is based on the Markovian approximation to the exact, noise-averaged stochastic Liouville-von Neumann equation, unravelled through the addition of stochastic environmental disturbance mimicking a measuring device. Under the thermalising influence of time independent coupling to the environment, the mean rate of entropy production vanishes asymptotically, indicating equilibrium. In contrast, a positive mean production of entropy as the system responds to time dependent coupling characterises the irreversibility of quantum measurement, and a comparison of its production for two coupling protocols, representing connection to and disconnection from the external measuring device, satisfies a detailed fluctuation theorem.
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Alipour, S., F. Benatti, F. Bakhshinezhad, M. Afsary, S. Marcantoni et A. T. Rezakhani. « Correlations in quantum thermodynamics : Heat, work, and entropy production ». Scientific Reports 6, no 1 (21 octobre 2016). http://dx.doi.org/10.1038/srep35568.
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Malouf, William T. B., Jader P. Santos, Luis A. Correa, Mauro Paternostro et Gabriel T. Landi. « Wigner entropy production and heat transport in linear quantum lattices ». Physical Review A 99, no 5 (6 mai 2019). http://dx.doi.org/10.1103/physreva.99.052104.
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de Oliveira, Mário J. « Stochastic quantum thermodynamics, entropy production, and transport properties of a bosonic system ». Physical Review E 97, no 1 (5 janvier 2018). http://dx.doi.org/10.1103/physreve.97.012105.
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Marconi, Umberto Marini Bettolo, Andrea Puglisi et Claudio Maggi. « Heat, temperature and Clausius inequality in a model for active Brownian particles ». Scientific Reports 7, no 1 (21 avril 2017). http://dx.doi.org/10.1038/srep46496.
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Abstract Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system’s Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems. Furthermore, by restricting the dynamical space to the first velocity moments of the local distribution function we derive a hydrodynamic description where local pressure, kinetic temperature and internal heat fluxes appear and are consistent with the previous thermodynamic analysis. The procedure also shows under which conditions one obtains the unified coloured noise approximation (UCNA): such an approximation neglects the fast relaxation to the active bath and therefore yields detailed balance and zero entropy production. In the last part, by using multiple time-scale analysis, we provide a constructive method (alternative to UCNA) to determine the solution of the Kramers equation and go beyond the detailed balance condition determining negative entropy production.
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Zicari, Giorgio, Baris Cakmak, Ozgur E. Mustecaplioglu et Mauro Paternostro. « On the role of initial coherence in the spin phase-space entropy production rate ». New Journal of Physics, 18 janvier 2023. http://dx.doi.org/10.1088/1367-2630/acb45b.
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Abstract Recent studies have pointed out the intrinsic dependence of figures of merit of thermodynamic relevance – such as work, heat and entropy production – on the amount of quantum coherences that is made available to a system. However, whether coherences hinder or enhance the value taken by such quantifiers of thermodynamic performance is yet to be ascertained. We show that, when considering entropy production generated in a process taking a finite-size bipartite quantum system out of equilibrium through local non-unitary channels, no general monotonicity relationship exists between the entropy production and degree of quantum coherence in the state of the system. A direct correspondence between such quantities can be retrieved when considering specific forms of open-system dynamics applied to suitably chosen initial states. Our results call for a systematic study of the role of genuine quantum features in the non-equilibrium thermodynamics of quantum processes.
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Ghoshal, Ahana, et Ujjwal Sen. « Heat current and entropy production rate in local non-Markovian quantum dynamics of global Markovian evolution ». Physical Review A 105, no 2 (17 février 2022). http://dx.doi.org/10.1103/physreva.105.022424.
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Mahault, Benoît, Evelyn Tang et Ramin Golestanian. « A topological fluctuation theorem ». Nature Communications 13, no 1 (31 mai 2022). http://dx.doi.org/10.1038/s41467-022-30644-6.
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AbstractFluctuation theorems specify the non-zero probability to observe negative entropy production, contrary to a naive expectation from the second law of thermodynamics. For closed particle trajectories in a fluid, Stokes theorem can be used to give a geometric characterization of the entropy production. Building on this picture, we formulate a topological fluctuation theorem that depends only by the winding number around each vortex core and is insensitive to other aspects of the force. The probability is robust to local deformations of the particle trajectory, reminiscent of topologically protected modes in various classical and quantum systems. We demonstrate that entropy production is quantized in these strongly fluctuating systems, and it is controlled by a topological invariant. We demonstrate that the theorem holds even when the probability distributions are non-Gaussian functions of the generated heat.
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Li, Yongwei, et Lei Li. « Hierarchical-environment-assisted non-Markovian and its effect on thermodynamic properties ». EPJ Quantum Technology 8, no 1 (15 avril 2021). http://dx.doi.org/10.1140/epjqt/s40507-021-00098-8.
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AbstractWe consider a microscopic collision model, i.e., a quantum system interacts with a hierarchical environment consisting of an auxiliary system and a reservoir. We show how the non-Markovian character of the system is influenced by the coupling strength of system-auxiliary system and auxiliary system-reservoir, coherence of environment and initial system-environment correlations. And we study the non-Markovianity induced by coherence of environment from the perspective of energy, further the relationship between information backflow and energy flux is obtained. Then we study the effect of non-Markovianity on thermodynamic properties. By studying the entropy change of system especially that from heat exchanges with the environment, we reveal the essence of entropy change between positive and negative values during non-Markovian evolution is due to the contribution of heat flux induced by coherence. And compared with the case of Markovian dynamics, we observe that the entropy production decreases in some specific time intervals under non-Markovian dynamics induced by the coupling strength. And this is different to the case of non-Markovianity caused by initial system-environment correlation, that we show the possibility of positive entropy production during the whole dynamics.
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Sohrab, Siavash H. « On a Scale-Invariant Model of Statistical Mechanics and the Laws of Thermodynamics ». Journal of Energy Resources Technology 138, no 3 (13 janvier 2016). http://dx.doi.org/10.1115/1.4032241.
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A scale-invariant model of statistical mechanics is applied to describe modified forms of zeroth, first, second, and third laws of classical thermodynamics. Following Helmholtz, the total thermal energy of the thermodynamic system is decomposed into free heat U and latent heat pV suggesting the modified form of the first law of thermodynamics Q = H = U + pV. Following Boltzmann, entropy of ideal gas is expressed in terms of the number of Heisenberg–Kramers virtual oscillators as S = 4 Nk. Through introduction of stochastic definition of Planck and Boltzmann constants, Kelvin absolute temperature scale T (degree K) is identified as a length scale T (m) that is related to de Broglie wavelength of particle thermal oscillations. It is argued that rather than relating to the surface area of its horizon suggested by Bekenstein (1973, “Black Holes and Entropy,” Phys. Rev. D, 7(8), pp. 2333–2346), entropy of black hole should be related to its total thermal energy, namely, its enthalpy leading to S = 4Nk in exact agreement with the prediction of Major and Setter (2001, “Gravitational Statistical Mechanics: A Model,” Classical Quantum Gravity, 18, pp. 5125–5142).
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Sparaciari, Carlo, Marcel Goihl, Paul Boes, Jens Eisert et Nelly Huei Ying Ng. « Bounding the resources for thermalizing many-body localized systems ». Communications Physics 4, no 1 (4 janvier 2021). http://dx.doi.org/10.1038/s42005-020-00503-1.
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AbstractUnderstanding under which conditions physical systems thermalize is a long-standing question in many-body physics. While generic quantum systems thermalize, there are known instances where thermalization is hindered, for example in many-body localized (MBL) systems. Here we introduce a class of stochastic collision models coupling a many-body system out of thermal equilibrium to an external heat bath. We derive upper and lower bounds on the size of the bath required to thermalize the system via such models, under certain assumptions on the Hamiltonian. We use these bounds, expressed in terms of the max-relative entropy, to characterize the robustness of MBL systems against externally-induced thermalization. Our bounds are derived within the framework of resource theories using the convex split lemma, a recent tool developed in quantum information. We apply our results to the disordered Heisenberg chain, and numerically study the robustness of its MBL phase in terms of the required bath size.
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Khan, K., Jailson Sales Araújo, W. F. Magalhães, Gabriel Aguilar et Bertúlio de Lima Bernardo. « Coherent energy fluctuation theorems : theory and experiment ». Quantum Science and Technology, 13 juin 2022. http://dx.doi.org/10.1088/2058-9565/ac781c.
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Abstract Fluctuation theorems (FT) reveal crucial properties about the nature of non-equilibrium dynamics by constraining the statistical distribution of quantities such as heat, work and entropy production. Here, we report theoretical and experimental results regarding two FT for a new quantity, named coherent energy, which is an energy form directly associated with the coherences of a quantum state. The FT are verified using the two-point measurement protocol with an all-optical setup in which the system information is encoded in the polarization of one photon of a pair. From the outcomes of our experiment we directly assess the energy probability distributions. We also demonstrate an universal bound on the energy of thermal states under the action of unitary operations, which could be the first step to establish an arrow of time for reversible processes.
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Abourabia, Aly M., et Amany Z. Elgarawany. « A Quantum Optical Approach to the effect of a Laser Mode on the Motion of Atomic Vapor by Varying the Field Coherence Angles ». Asian Journal of Research and Reviews in Physics, 25 mai 2021, 25–47. http://dx.doi.org/10.9734/ajr2p/2021/v4i230140.
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We follow theoretically the motion of the sodium atoms in vapor state under the influence of a laser mode in (1 + 1) D, which is achieved by introducing different optical filters. In the Dirac interaction representation, the equations of motion are represented via the Bloch form together with the Pauli operators to find the elements of the density matrix of the system. The emergence of the principle of coherence in varying the angles of the laser mode permits the evaluation of the average force affecting the atoms' acceleration or deceleration, and hence the corresponding velocities and temperatures are investigated. The atomic vapor is introduced in a region occupied by a heat bath presented by the laser field, such that the state of the atomic vapor is unstable inside the system due to the loss or gain of its kinetic energy to or from the laser field. This instability is studied by finding the eigenvalues of the system's entropy. Resorting to the assumption of Botin, Kazantsev, and Pusep, who issued in the presence of the weak and strong spontaneous emission, a coupling between the mean numbers of photons in terms of time, which allows the evaluation of the rate of entropy production of the system under study. No singularities are found throughout the process of equations solving and other calculations. Resorting to symbolic software, a set of figures illustrating the nonlinear behavior in the dynamics of the problem is present. In this paper, we introduce a theoretical study of the effect of two-counter propagation traveling plane waves on the motion of the sodium atoms in the vapor state by varying the coherence angles to investigate the atomic behavior. Good agreements are found with previous studies.