热浴中标量场的非平衡动力学

Fluctuation-Dissipation Relation for Open Quantum Systems in Nonequilibrium Steady State

Continuing our work on the nature and existence of fluctuation-dissipation relations (FDR) in linear and nonlinear open quantum systems [1-3], here we consider such relations when a linear system is in a nonequilibrium steady state (NESS). With the model of two-oscillators (considered as a short harmonic chain with the two ends) each connected to a thermal bath of different temperatures we find that when the chain is fully relaxed due to interaction with the baths, the relation that connects the noise kernel and the imaginary part of the dissipation kernel of the chain in one bath does not ass…

Nonequilibrium Nonlinear Open Quantum Systems I. Functional Perturbative Analysis of a Weakly Anharmonic Oscillator

We introduce a functional perturbative method for treating weakly nonlinear systems coupled with a quantum field bath. We demonstrate using this method to obtain the covariance matrix elements and the correlation functions of a quantum anharmonic oscillator interacting with a heat bath. We identify a fluctuation-dissipation relation based on the nonequilibrium dynamics of this nonlinear open quantum system. To establish its connection with dynamical equilibration, we further examine the energy flows between the anharmonic oscillator and the bath field. The vanishing of the net flow {is an indi…

耦合量子系统的非平衡动力学

Nonequilibrium Dynamics of Coupled Quantum Systems

利用Liouville-vonNeumann方法分析了耦合量子振子在不同含时猝灭下的非平衡动力学。我们考虑模型的量子振荡器的相互作用，是完全可溶的情况下，突然和顺利淬火。给出了一个量子振子与无穷多个其它振子（一个浴）耦合问题的数密度随时间的演化和最终平衡分布。

相对运动通过热浴作为热力学资源

Relativistic motion through a thermal bath as a thermodynamic resource

通过相对运动，局部量子系统被驱动进入非吉布斯稳态，其中一类可作为噪声随机钟，另一类具有非平衡自由能，可用于功提取或存储。

Fluctuation-Dissipation Relation for a Quantum Brownian Oscillator in a Parametrically Squeezed Thermal Field

In this paper we study the nonequilibrium evolution of a quantum Brownian oscillator, modeling the internal degree of freedom of a harmonic atom or an Unruh-DeWitt detector, coupled to a nonequilibrium, nonstationary quantum field and inquire whether a fluctuation-dissipation relation can exist after/if it approaches equilibration. This is a nontrivial issue since a squeezed bath field cannot reach equilibration and yet, as this work shows, the system oscillator indeed can, which is a necessary condition for FDRs. We discuss three different settings: A) The bath field essentially remains in a …

Fluctuation-Dissipation Relation from the Nonequilibrium Dynamics of a Nonlinear Open Quantum System

Continuing our inquiry into the conditions when fluctuation-dissipation relations (FDR) may appear in the context of nonequilibrium dynamics of open quantum systems (over and beyond the conventional FDR from linear response theory) we turn to nonGaussian systems and consider this issue for an anharmonic oscillator interacting with a scalar quantum field bath. We present the general {nonperturbative} expressions for the rate of energy (power) exchange between the anharmonic oscillator and the thermal bath. For the cases that a stable final equilibrium state exists, and the nonstationary compone…

Energy Transport between Strange Quantum Baths

Energy transport in quantum many-body systems with well defined quasiparticles has recently attracted interest across different fields, including out of equilibrium conformal field theories, one dimensional quantum lattice models and holographic matter. Here we study energy transport between \emph{strange quantum baths} without quasiparticles, made by two Sachdev-Ye-Kitaev (SYK) models at temperatures $T_L\neq T_R$ and connected by a Fermi-Liquid system. We obtain an exact expression for the nonequilibrium energy current, valid in the limit of large bath and system size and for any system-bath…

热浴中的一维Dirac振子

One-dimensional Dirac oscillator in a thermal bath

我们分析了热浴中的一维狄拉克振子。我们发现，在更高的温度下，热容是一维谐振子热容的两倍。

耦合到热浴的Sachdev-Ye-Kitaev模型中的可调量子混沌

Tunable Quantum Chaos in the Sachdev-Ye-Kitaev Model Coupled to a Thermal Bath

Sachdev-Ye-Kitaev（SYK）模型描述了具有随机相互作用的Majorana费米子，它表现出许多有趣的性质，如非费米液体行为、量子混沌、涌现共形对称性和全息对偶。在这里，我们考虑一个SYK模型或SYK模型链的$N$马约拉纳费米子模式耦合到另一个SYK模型与$N^2$马约拉纳费米子模式，其中后者有更多的自由度，并发挥作用的热浴。对于一个单一的SYK模型耦合到热浴，我们表明，虽然李雅普诺夫指数仍然是成比例的温度，它单调下降，从$2π/β$（$β=1/(k_BT)$，$T$是温度）为零的耦合强度的热浴增加。对于一个链的SYK模型，当它们均匀地耦合到热浴，我们表明，蝴蝶速度显示交叉从$\sqrt{T}$ -依赖在相对较高的温度下的线性$T$ -依赖在低温下，与交叉温度也控制的耦合强度的热浴。如果仅SYK链的末端耦合到热浴，则该模型可以引入李雅普诺夫指数和蝴蝶速度两者的空间依赖性。我们的模型提供了规范的例子，在混沌模型的热化研究。

热浴中的匀加速观测器

Uniformly accelerated observer in a thermal bath

我们研究了在热浴中匀速运动的观测者在平坦时空中的量子场。特别地，当量子场的态是温度为$T^\prime$的热浴时，我们得到了加速度为$a = 2πT$的匀加速观测者的约化密度矩阵的精确封闭表达式.我们发现，密度矩阵有一个简单的形式与有效的配分函数$Z$的产品，$Z = Z_T Z_{T^\prime}$，对应于温度$T$和$T^\prime$的两个热配分函数，因此不是热的，即使当$T = T^\prime$。我们发现，即使配分函数有一个产品结构，两个热浴，事实上，相互作用的系统，虽然在高频率限制$ω_k \gg T$和$ω_k \gg T^\prime$，被发现的相互作用，成为次主导。我们进一步证明，由此产生的光谱的Rindler粒子可以解释在自发和受激发射由于背景热浴。密度矩阵也被发现是对称的，在加速温度$T$和热浴温度$T^\prime$，表明热力学实验本身不能区分由于$T$和那些由于$T^\prime$的热效应。纠缠熵与约化密度矩阵（与背景贡献的Davies-Unruh浴删除）示出满足，在$ω_k \gg T^\prime$限制，热力学关系的形式$T δS = δE$的第一定律，其中$δE$是对应于约化密度矩阵和背景Davies-Unruh浴的能量的差异。的影响进行了讨论。

Entanglement harvesting of accelerated detectors versus static ones in a thermal bath

We make a detailed comparison between entanglement harvesting for uniformly accelerated detectors in vacuum and static ones in a thermal bath at the Unruh temperature and find that, for a small energy gap relative to the Heisenberg energy of the detectors, static detectors in the thermal bath can harvest more entanglement and possess a comparatively larger harvesting-achievable range than the uniformly accelerated ones; however, as the energy gap grows sufficiently large, the uniformly accelerated detectors are instead likely to harvest more entanglement and possess a relatively larger harvest…

热浴对加速参考系中 Pancharatnam-Berry 相位的影响

Influence of thermal bath on Pancharatnam-Berry phase in an accelerated frame

本文研究匀加速原子的 Pancharatnam-Berry 相位，发现场的热性质及 Unruh 热浴与真实热浴的交换对称性会影响相位，但实验所需高温超出当前技术能力。