关于非平衡量子场的朗之万描述
On the Langevin description of nonequilibrium quantum fields
摘要：
考虑实量子标量场的非平衡动力学。我们证明了一个虚构的朗之万过程的统计和光谱两点函数的精确演化方程的形式等价性，并研究了当地马尔可夫动力学是一个有效的近似条件。在量子场论中，记忆核和噪声相关器通常表现出长时间幂律，因此是高度非局部的，从而质疑局部描述的可能性。我们表明，尽管这一事实，有一个有限的时间范围内，当地的描述是准确的。这要求理论是（有效地）弱耦合的。我们举例说明使用这样的本地描述的退相干和熵产生的研究在量子场论。
英文摘要：
We consider the non-equilibrium dynamics of a real quantum scalar field. We show the formal equivalence of the exact evolution equations for the statistical and spectral two-point functions with a fictitious Langevin process and examine the conditions under which a local Markovian dynamics is a valid approximation. In quantum field theory, the memory kernel and the noise correlator typically exhibit long time power laws and are thus highly non-local, thereby questioning the possibility of a local description. We show that despite this fact, there is a finite time range during which a local description is accurate. This requires the theory to be (effectively) weakly coupled. We illustrate the use of such a local description for studies of decoherence and entropy production in quantum field theory.
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