Sustaining a temperature difference

Compatibility of Carnot efficiency with finite power in an underdamped Brownian Carnot cycle in small temperature-difference regime

We study the possibility of achieving the Carnot efficiency in a finite-power underdamped Brownian Carnot cycle. Recently, it was reported that the Carnot efficiency is achievable in a general class of finite-power Carnot cycles in the vanishing limit of the relaxation times. Thus, it may be interesting to clarify how the efficiency and power depend on the relaxation times by using a specific model. By evaluating the heat-leakage effect intrinsic in the underdamped dynamics with the instantaneous adiabatic processes, we demonstrate that the compatibility of the Carnot efficiency and finite pow…

Stirling engine operating at low temperature difference

The paper develops the dynamics and thermodynamics of Stirling engines that run with temperature differences below 100 0C. The working gas pressure is analytically expressed using an alternative thermodynamic cycle. The shaft dynamics is studied using its rotational equation of motion. It is found that the initial volumes of the cold and hot working gas play a non-negligible role in the functioning of the engine.

Maxwell's Conjecture of the Demon creating a Temperature Difference is False

We argue that Maxwell's demon is incapable of creating a nonzero temperature difference. Hence, it does not destroy equilibrium and the second law is never at risk, contrary to the claim by Maxwell and accepted by many. It is therefore remarkable that despite this, the demon paradox has been a valuable source of new ideas. We use two independent arguments, one using classical equilibrium thermodynamics by extending Brillouin's approach, and the other one using equilibrium statistical mechanics and the central limit theorem.

Temperature Integration: an efficient procedure for calculation of free energy differences

We propose a method, Temperature Integration, which allows an efficient calculation of free energy differences between two systems of interest, with the same degrees of freedom, which may have rough energy landscapes. The method is based on calculating, for each single system, the difference between the values of lnZ at two temperatures, using a Parallel Tempering procedure. If our two systems of interest have the same phase space volume, they have the same values of lnZ at high-T, and we can obtain the free energy difference between them, using the two single-system calculations described abo…

惯性活性哑铃共存相中平移与旋转温度差

Translational and Rotational Temperature Difference in Coexisting Phases of Inertial Active Dumbbells

研究揭示了活性哑铃在共存相中平移与旋转惯性对温度差的影响，发现温度差异随惯性及活动性增强而变化，为非平衡热力学提供新视角。

Nonlinear dynamics analysis of a low-temperature-differential kinematic Stirling heat engine

The low-temperature-differential (LTD) Stirling heat engine technology constitutes one of the important sustainable energy technologies. The basic question of how the rotational motion of the LTD Stirling heat engine is maintained or lost based on the temperature difference is thus a practically and physically important problem that needs to be clearly understood. Here, we approach this problem by proposing and investigating a minimal nonlinear dynamic model of an LTD kinematic Stirling heat engine. Our model is described as a driven nonlinear pendulum where the motive force is the temperature…

Equilibrium Equality for Free Energy Difference

Jarzynski Equality (JE) and the thermodynamic integration method are conventional methods to calculate free energy difference (FED) between two equilibrium states with constant temperature of a system. However, a number of ensemble samples should be generated to reach high accuracy for a system with large size, which consumes a lot computational resource. Previous work had tried to replace the non-equilibrium quantities with equilibrium quantities in JE by introducing a virtual integrable system and it had promoted the efficiency in calculating FED between different equilibrium states with con…

Motility-induced temperature difference in coexisting phases

In nature, objects which are in thermal contact with each other, usually approach the same temperature, unless a heat source (or sink) cherishes a persistent flow of heat. Accordingly, in a well-isolated apartment flat, most items are at a similar temperature. This is a general consequence of equilibrium thermodynamics, requiring coexisting phases to have identical temperatures. Opposing this generic situation, here we identify a system showing different temperatures in coexisting phases, which are separated from each other by a sharp and persistent temperature gradient. Thermodynamically, suc…

Two-temperature statistics of free energies in (1+1) directed polymers

The joint statistical properties of two free energies computed at two different temperatures in {\it the same sample} of $(1+1)$ directed polymers is studied in terms of the replica technique. The scaling dependence of the reduced free energies difference ${\cal F} = F(T_{1})/T_{1} - F(T_{2})/T_{2}$ on the two temperatures $T_{1}$ and $T_{2}$ is derived. In particular, it is shown that if the two temperatures $T_{1} \, < \, T_{2}$ are close to each other the typical value of the fluctuating part of the reduced free energies difference ${\cal F}$ is proportional to $(1 - T_{1}/T_{2})^{1/3}$. It…

Nonequilibrium Generalised Langevin Equation for the calculation of heat transport properties in model 1D atomic chains coupled to two 3D thermal baths

We use a Generalised Langevin Equation (GLE) scheme to study the thermal transport of low dimensional systems. In this approach, the central classical region is connected to two realistic thermal baths kept at two different temperatures [H. Ness et al., Phys. Rev. B {\bf 93}, 174303 (2016)]. We consider model Al systems, i.e. one-dimensional atomic chains connected to three-dimensional baths. The thermal transport properties are studied as a function of the chain length $N$ and the temperature difference $ΔT$ between the baths. We calculate the transport properties both in the linear response …