Energy and Heat Fluctuations in a Temperature Quench

Fluctuations of energy and heat are investigated during the relaxation following the instantaneous temperature quench of an extended system. Results are obtained analytically for the Gaussian model and for the large N model quenched below the critical temperature T_C. The main finding is that fluctuations exceeding a critical threshold do condense. Though driven by a mechanism similar to that of Bose-Einstein condensation, this phenomenon is an out-of-equilibrium feature produced by the breaking of energy equipartition occurring in the transient regime. The dynamical nature of the transition is illustrated by phase diagrams extending in the time direction.     

Metastability for a Stochastic Dynamics with a Parallel Heat Bath Updating Rule

We consider the problem of metastability for a stochastic dynamics with a parallel updating rule with single spin rates equal to those of the heat bath for the Ising nearest neighbors interaction. We study the exit from the metastable phase, we describe the typical exit path and evaluate the exit time. We prove that the phenomenology of metastability is different from the one observed in the case of the serial implementation of the heat bath dynamics. In particular we prove that an intermediate chessboard phase appears during the excursion from the minus metastable phase toward the plus stable phase.     

Effects of Dissipations on Fluctuations in an RLC Circuit with a Source in a Thermal Bath

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Effects of Dissipations on Fluctuations in an RLC Circuit with a Source in a Thermal Bath

It is presented a quantum theory for an RLC circuit with a source in a thermal bath. It establishs and solves the equation of motion for the density operator of the circuit and discusses the effects of the dissipations on the fluctuations of the charge and of the magnetic flux in the circuit.     

Analysis and Experiments for a Computational Model of a Heat Bath

A question of some interest in computational statistical mechanics is whether macroscopic quantities can be accurately computed without detailed resolution of the fastest scales in the problem. To address this question a simple model for a distinguished particle immersed in a heat bath is studied (due to Ford and Kac). The model yields a Hamiltonian system of dimension 2N+2 for the distinguished particle and the degrees of freedom describing the bath. It is proven that, in the limit of an infinite number of particles in the heat bath (N), the motion of the distinguished particle is governed by a stochastic differential equation (SDE) of dimension 2. Numerical experiments are then conducted on the Hamiltonian system of dimension 2N+2 (N1) to investigate whether the motion of the distinguished particle is accurately computed (i.e., whether it is close to the solution of the SDE) when the time step is small relative to the natural time scale of the distinguished particle, but the product of the fastest frequency in the heat bath and the time step is not small—the underresolved regime in which many computations are performed. It is shown that certain methods accurately compute the limiting behavior of the distinguished particle, while others do not. Those that do not are shown to compute a different, incorrect, macroscopic limit.     

Heat Fluctuations and a generalized Gibbs equation

Starting from a generalized Gibbs equation and from the Einstein formula for the probability of fluctuations, we obtain the correlation function of heat fluctuations.     

Anomalous Fluctuations for a Perturbed Hamiltonian System with Exponential Interactions

A one-dimensional Hamiltonian system with exponential interactions perturbed by a conservative noise is considered. It is proved that energy superdiffuses and upper and lower bounds describing this anomalous diffusion are obtained.     

The Quantum Otto Heat Engine with a Relativistically Moving Thermal Bath

International Journal of Theoretical Physics - We investigate the quantum thermodynamic cycle of a quantum heat engine carrying out an Otto thermodynamic cycle. We use the thermal properties of a...     

组合式隔热陶瓷短杆高温SHPB实验技术

讨论和分析了当前高温分离式霍普金森压杆(SHPB)实验技术,为了获得材料在高温下可靠的动态力学性能,建立了一套在压杆和试件之间添加隔热陶瓷短杆的高温SHPB实验系统。相比于传统接触式高温SHPB方案,该系统可以使用在更高的冲击载荷和温度下,与机械对杆方案相比,实验装置及其控制要简便许多。结合有限元模拟,对陶瓷短杆及温度场对压杆中应力波传播的影响进行了相应的评估,并利用这套实验系统得到了800℃下HR2抗氢钢的动态压缩应力-应变曲线。     

How Hot Can a Heat Bath Get?

We study a model of two interacting Hamiltonian particles subject to a common potential in contact with two Langevin heat reservoirs: one at finite and one at infinite temperature. This is a toy model for ‘extreme’ non-equilibrium statistical mechanics. We provide a full picture of the long-time behaviour of such a system, including the existence/non-existence of a non-equilibrium steady state, the precise tail behaviour of the energy in such a state, as well as the speed of convergence toward the steady state. Despite its apparent simplicity, this model exhibits a surprisingly rich variety of long time behaviours, depending on the parameter regime: if the surrounding potential is ‘too stiff’, then no stationary state can exist. In the softer regimes, the tails of the energy in the stationary state can be either algebraic, fractional exponential, or exponential. Correspondingly, the speed of convergence to the stationary state can be either algebraic, stretched exponential, or exponential. Regarding both types of claims, we obtain matching upper and lower bounds.     

Two-Level Dipolar System in a Heat Bath: High-Pump Power Effects in the Nonlinear Optical Responses

Using the four-wave mixing spectroscopy, we analyze the nonlinear optical properties in a strongly driven two-level system, using a perturbative treatment where, the pump field is considered at all orders, second order in the probe, and first order for the signal field, when the stochastic effects of the solvent are considered. Significant variations in the nonlinear optical properties due mainly to changes in the probe intensity, chemical concentrations, and transversal relaxation times are observed.     

Equilibrium Fluctuations for a System of Harmonic Oscillators with Conservative Noise

We investigate the harmonic chain forced by a multiplicative noise, the evolution is given by an infinite system of stochastic differential equations. Total energy and deformation are preserved, the conservation of momentum is destroyed by the noise. Gaussian product measures are the extremal stationary states of this model. Equilibrium fluctuations of the conserved fields at a diffusive scaling are described by a couple of generalized Ornstein-Uhlenbeck processes. 1991 Mathematics Subject Classification: Primary 60K31, secondary 82C22 Partially supported by Hungarian Science Foundation Grant T37685, the European Science Foundation Project RDSES, and by the ACI-NIM 168 ‘Transport hors équilibre.’     

Entanglement Evolution of a 2-Qutrit System Interacting with a Fermionic Bath

Based on the algebraic entanglement measure proposed [G. Vidal et al., Phys. Rev. A 65 (2002) 032314],we study the entanglement evolution of both pure quantum states and mixed ones of 2-qutrit system in a symmetrybroken environment consisting of a fermionic bath. Entanglement of states will decrease or remain constant under the influence of environment, and the class of states which remain unchanged has been found out.     

Entanglement Evolution of a 2-Qutrit System Interacting with a Fermionic Bath

Based on the algebraic entanglement measure proposed [G. Vidal et al., Phys. Rev. A 65 （2002） 032314],we study the entanglement evolution of both pure quantum states and mixed ones of 2-qutrit system in a symmetrybroken environment consisting of a fermionic bath. Entanglement of states will decrease or remain constant under the influence of environment, and the class of states which remain unchanged has been found out.     

Fractional Kinetics in Kac–Zwanzig Heat Bath Models

We study a variant of the Kac–Zwanzig model of a particle in a heat bath. The heat bath consists of n particles which interact with a distinguished particle via springs and have random initial data. As n → ∞ the trajectories of the distinguished particle weakly converge to the solution of a stochastic integro-differential equation—a generalized Langevin equation (GLE) with power-law memory kernel and driven by 1/f ^α -noise. The limiting process exhibits fractional sub-diffusive behaviour. We further consider the approximation of non-Markovian processes by higher-dimensional Markovian processes via the introduction of auxiliary variables and use this method to approximate the limiting GLE. In contrast, we show the inadequacy of a so-called fractional Fokker–Planck equation in the present context. All results are supported by direct numerical experiments.     

Decoherence of a Quantum Nonlinear Oscillator Under a Non-zero Temperature Thermal Bath

The characteristic time τ_D for decoherence process of a quantum nonlinear oscillator system under a non-zero temperature thermal bath is studied by expanding the linear entropy. By numerical analysis, it is shown that at a non-zero temperature, the quantum coherence decays much faster than at zero temperature. Moreover, the non-zero temperature thermal bath will bring a crucial suppression to the quantum effects of the observables, which causes these quantum effects to become unable to persist up to the Ehrenfest time but is insufficient to destroy the quantum-classical transition.     

盐浴复合热处理技术氮化盐研究与测定

盐浴复合热处理技术是一种新型表面处理技术,能增强工件的耐磨性、耐腐蚀性和耐疲劳性,在金属表面处理中得到广泛的应用。氮化盐中氰酸根、氰化物和铁离子的含量对该热处理技术的质量控制十分重要,因此需要准确测定该三成分的含量以保证金属表面处理的质量。针对目前业内所采用的化学滴定法难以满足自动化分析的技术要求,基于分光光度法,采用510,620和697 nm三个不同波长的单色LED光源、耦合光纤、光电二极管搭建了一台半自动氮化盐三参数分析实验装置,实现氰酸根、氰化物和铁离子的快速准确测试。该半自动实验装置除了光路系统外,还有搅拌控制系统、恒温控制系统、数据采集电路系统。氰酸盐检测采用间接检测方法,先通过化学方法把氰酸根转变为铵根,再根据标准GB 7481-1987水质铵的测定-水杨酸分光光度法,通过对铵离子的测定（检测波长697 nm）间接测量氰酸根。氰化物检测依据标准HJ484-2009水质氰化物的测定-异烟酸-巴比妥酸分光光度法（检测波长620 nm）。铁离子含量的检测依据标准HJ345-2007水质铁的测定-邻菲啰啉分光光度法,光谱检测特征波长为510 nm。对LED光源光强稳定性进行了测试,LED光源一开始工作光强即达到稳定值;测试了耦合光纤对LED光源的光谱影响,单色光源通过耦合光纤和单光纤的光谱没有发生变化,只是通过耦合光纤后光强值有所降低;测试了搅拌对LED光源光强稳定性影响,搅拌系统对光学系统没有影响。利用实验装置测量出不同浓度氰酸根标准样品氰酸钾、氰根标准样品氰化钾、铁离子标准样品硫酸亚铁的吸光度,基于朗伯比尔定律,建立氰酸根、氰化物和铁离子标样的拟合曲线,其线性相关度R2分别为0.990 7,0.999 6和0.998 1,线性度高;氰酸根、氰根和铁离子的预测样品均值最大相对误差和最大相对标准偏差RSD分别为4.53%和1.04%,2.29%和0.79%,4.2%和0.7%,说明三样品测试结果准确性高、重复性好;氰酸根、氰根和铁离子的最低检出限LOD分别为0.017,0.009和0.005 mg·L-1。比较了用设计的氮化盐三成分半自动检测装置与传统化学滴定法测得的氮化盐样品中的氰酸根、氰化物和铁离子含量,设计的检测系统测试结果优于传统的化学滴定法,其中测试的氮化盐样品的氰酸根、氰化物和铁离子均值相对误差和相对标准方差RSD分别为4.17%和0.69%,1%和0.58%,4%和0.29%。各项测试结果均达到设计要求,为盐浴复合热处理技术氮化盐三成分半自动分析仪提供了理论和技术支持。论文搭建的氮化盐三成分半自动检测装置的光路系统采用单色LED光源、多进一出耦合光纤对光源分光,实现多参数的快速准确检测,整套光学检测系统无任何活动部件,大大降低了光学检测系统带来的系统误差,保证了测试的准确度和重复性。     

热库诱导的两比特量子纠缠与量子关联

对比研究了处于热库中的两量子比特的量子纠缠和量子关联随时间的演化。数值模拟的结果表明,尽管热库几乎总能诱导两量子比特的量子纠缠与量子关联,但二者的动力学演化并不完全相同。在与热库的相互作用中,两比特初始形成量子纠缠,随后纠缠逐渐消失,两比特形成纠缠以外的量子关联并得到维持。由此看出,相比于量子纠缠,量子关联对消相干的影响表现得更为稳健。