Nonequilibrium thermodynamics in cavity optomechanics

Classical thermodynamics has been a great achievement in dealing with systems that are in equilibrium or near equilibrium.As an emerging field,nonequilibrium thermodynamics provides a general framework for understanding the nonequilibrium processes,particularly in small systems that are typically far-from-equilibrium and are dominated by thermal or quantum fluctuations.Cavity optomechanical systems hold great promise among the various experimental platforms for studying nonequilibrium thermodynamics owing to their high controllability,excellent mechanical performance,and ability to operate deep in the quantum regime.Here,we present an overview of the recent advances in nonequilibrium thermodynamics with cavity optomechanical systems.The experimental results in entropy production assessment,fluctuation theorems,heat transfer,and heat engines are highlighted.

Nonequilibrium Thermodynamic and Dissipative Structure Mechanism of Fluidized Beds

Fluidized beds are nonlinear dynamic systems that exchange mass and energy with outside. They are governed not only byfluid dynamics, but by thermodynamics, especially the second law of thermodynamics as well. According to Prigogine's dissipative structure theory, the following have been concluded: (l) a fixed bed is on thermodynamic blanch, and bubbling, turbulent and fast beds areon the dissipatve structure branches. (2) Entropy in fluidized beds is divided into tWo parts: entropy production and entropy flux. The latter increases with gas velocity and decreases with pressure of the systems. That means the entropy of a system may reduce and the systemwith higher gas velocity behaves as dissipative structure characteristics. (3) For a giVen velocity, a fluidized bed operates stably on thewhole, but it is unstable to local gas-solid phases. The unstable phases are described by fluid dynamic equations, While the minimum ofsystem energy function assures whole stability of the system. (4) A transition criterion of a bubbling bed is derived from Prigogine's stability theory.

Impact of counter-rotating-wave term on quantum heat transfer and phonon statistics in nonequilibrium qubit–phonon hybrid system

Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.

A polaron theory of quantum thermal transistor in nonequilibrium three-level systems

We investigate the quantum thermal transistor effect in nonequilibrium three-level systems by applying the polarontransformed Redfield equation combined with full counting statistics.The steady state heat currents are obtained via this unified approach over a wide region of system–bath coupling,and can be analytically reduced to the Redfield and nonequilibrium noninteracting blip approximation results in the weak and strong coupling limits,respectively.A giant heat amplification phenomenon emerges in the strong system–bath coupling limit,where transitions mediated by the middle thermal bath are found to be crucial to unravel the underlying mechanism.Moreover,the heat amplification is also exhibited with moderate coupling strength,which can be properly explained within the polaron framework.

Oscillatory Shannon entropy in the process of equilibration of nonequilibrium crystalline systems

We present a study of the equilibration process of some nonequilibrium crystalline systems by means of molecular dynamics simulation technique. The nonequilibrium conditions are achieved in the systems by randomly defining velocity components of the constituent atoms. The calculated Shannon entropy from the probability distribution of the kinetic energy among the atoms at different instants during the process of equilibration shows oscillation as the system relaxes towards equilibrium. Fourier transformations of these oscillating Shannon entropies reveal the existence of Debye frequency of the concerned system.

Fluid and Osmotic Pressure Balance and Volume Stabilization in Cells Dedicated to Professor Karl Stark Pister for his 95th birthday

A fundamental problem for cells with their fragile membranes is the control of their volume.The primordial solution to this problem is the active transport of ions across the cell membrane to modulate the intracellular osmotic pressure.In this work,a theoretical model of the cellular pump-leak mechanism is proposed within the general framework of linear nonequilibrium thermodynamics.The model is expressed with phenomenological equations that describe passive and active ionic transport across cell membranes,supplemented by an equation for the membrane potential that accounts for the electrogenicity of the ionic pumps.For active ionic transport,the model predicts that the intracellular fluid pressure will be balanced by the osmotic pressure and a new pressure component that arises from the active ionic fluxes.A model for the pump-leak mechanism in an idealized human cell is introduced to demonstrate the applicability of the proposed theory.

Detection of multi-spin interaction of a quenched XY chain by the average work and the relative entropy

We investigate the nonequilibrium thermodynamics of a quenched XY spin chain with multi-spin interaction in a transverse field.The analytical expressions of both the average work and the relative entropy are obtained under different quenching parameters.The influences of the system parameters on the nonequilibrium thermodynamics are investigated.We find that at finite temperature the critical phenomenon induced by the multi-spin interaction and the external field can be revealed by the properties of the system nonequilibrium thermodynamics.In addition,our results indicate that the average work and the relative entropy can be used to detect both the existence and strength of the multi-spin interaction in the nonequlibrium system.

An Interval-valued Approach to Calculation ofNonequilibriumThermodynamics with Imprecise Information

The research of the imprecision of a nonequilibrium thermodynamic system is justifiedby the structural and parametric uncertainties of such systems. The paper gives an interval-valuedformulation of the phenomenological equations and shows a realistic approach for studying the entropyproduction in Physical systems, the time trajectories of chemical reactions, etc. Using algorithms derivedfor special reaction systems, bundles of time trajectories with prescribed boundary possibility measuresare calculated.

Influence of the tangential velocity on the compressible Kelvin–Helmholtz instability with nonequilibrium effects

Kelvin–Helmholtz(KH)instability is a fundamental fluid instability that widely exists in nature and engineering.To better understand the dynamic process of the KH instability,the influence of the tangential velocity on the compressible KH instability is investigated by using the discrete Boltzmann method based on the nonequilibrium statistical physics.Both hydrodynamic and thermodynamic nonequilibrium(TNE)effects are probed and analyzed.It is found that,on the whole,the global density gradients,the TNE strength and area firstly increase and decrease afterwards.Both the global density gradient and heat flux intensity in the vertical direction are almost constant in the initial stage before a vortex forms.Moreover,with the increase of the tangential velocity,the KH instability evolves faster,hence the global density gradients,the TNE strength and area increase in the initial stage and achieve their peak earlier,and their maxima are higher for a larger tangential velocity.Physically,there are several competitive mechanisms in the evolution of the KH instability.(i)The physical gradients increase and the TNE effects are strengthened as the interface is elongated.The local physical gradients decrease and the local TNE intensity is weakened on account of the dissipation and/or diffusion.(ii)The global heat flux intensity is promoted when the physical gradients increase.As the contact area expands,the heat exchange is enhanced and the global heat flux intensity increases.(iii)The global TNE intensity reduces with the decreasing of physical gradients and increase with the increasing of TNE area.(iv)The nonequilibrium area increases as the fluid interface is elongated and is widened because of the dissipation and/or diffusion.

Dielectric properties of human diabetic blood: Thermodynamic characterization and new prospective for alternative diagnostic techniques

In this paper,we will show the possibility of studying physical properties and irreversible phenomena that occur in blood by applying the dielectric Kluitenberg's nonequilibrium thermodynamic theory.Namely,we shall use some recent extensions of this theory that allow to infer its main characteristic parameters from experimental measures.Applying these results to the study of normal and diabetic blood we show,by comparing them,that it is possible to determine the difference,in some details,of the amount of particular phenomena occurring inside them and give a biological meaning to these phenomena.Moreover,observing a correspondence between a particular value of the frequency for which state coefficients are equal and glucose levels we introduce an alternative diagnostic method to measure the values of the glucose in the blood by determining only this frequency value.The thermodynamic description will be completed by determining the trend of the entropy production.

The intrinsic nature of materials failure and the global non-equilibrium energy criterion

Materials failure under some sort of loading is a well-known natural phenomenon,and the reliable prediction of materials failure is the most important key issue for many different kinds of engineering structures based on their safety considerations.In this research,instead of establishing empirical models,the material failure process was modeled as a nonequilibrium process based on the microstructural mechanism.Then,the evolution equations were established and the stability analysis was carried out to obtain the critical conditions for the materials failure.It was found that the material strength was a global property in nature,and the commonly used local criteria based on the most dangerous point failure were not the rational assumption.Based on the idea,some examples were considered,such as the size effect of the material strength,the strength of the polycrystalline metals,the stress-strain relationship of the ultrafine crystalline metal with nanoscale growth twins,the strength of lithium niobite crystal specimens with notches.All of the theoretical predictions gave reasonable results compared with the experimental data.

Fluctuation theorem for entropy production in a chemical reaction channel

Fluctuation theorem for entropy production in a mesoscopic chemical reaction network is discussed. When the system size is sufficiently large, it is found that, by defining a kind of coarse-grained dissipation function, the entropy production in a reversible reaction channel can be approximately described by a type of detailed fluctuation theorem. Such a fluctuation relation has been successfully tested by direct simulations in a linear reaction model consisting of two reversible channels and in an oscillatory model wherein only one channel is reversible.

Discrete Boltzmann model for implosion- and explosion- related compressible flow with spherical symmetry

To kinetically model implosion- and explosion-related phenomena, we present a theoretical framework for constructing a discrete Boltzmann model （DBM） with spherical symmetry in spherical coordinates. To achieve this goal, a key technique is to use local Cartesian coordinates to describe the particle velocity in the kinetic model. Therefore, geometric effects, such as divergence and convergence, are described as a ＂force term＂. To better access the nonequilibrium behavior, even though the corre- sponding hydrodynamic model is one-dimensional, the DBM uses a discrete velocity model （DVM） with three dimensions. A new scheme is introduced so that the DBM can use the same DVM regard- less of whether or not there are extra degrees of freedom. As an example, a DVM with 26 velocities is formulated to construct the DBM at the Navier-Stokes level. Via the DBM, one can study simulta- neously the hydrodynamic and thermodynamic nonequilibrium behaviors in implosion and explosion processes that are not very close to the spherical center. The extension of the current model to a multiple-relaxation-time version is straightforward.