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arXiv 1107.0668hep-phnucl-th
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强场系统中量子涨落的作用:光谱性质和热化

Role of quantum fluctuations in a system with strong fields: Spectral properties and Thermalization

T. Epelbaum, F. Gelis

摘要:

在以前的工作[arXiv:1009.4363]中,我们研究了具有四次耦合的标量场的演化,该场由经典源驱动,使其达到非微扰的大值。在耦合的首阶,该系统的演化由场运动方程的经典解给出。然而,这个系统是受一个参数共振,导致长期的分歧,在高阶修正物理观测。我们已经提出了一个方案,所有领先的长期条款的resum:这remation导致有限的结果在任何时候,我们还观察到,它使系统的压力张量放松到其平衡值。在本文中,我们继续研究这个系统,通过查看其动力学的细节。我们首先计算它的谱函数在各个阶段的演变,我们观察到,经过一个相当短的瞬态时间有明确的大质量准粒子。然后,我们考虑这些准粒子的动量分布的时间演化,我们表明,由参数共振为主的阶段后,这个分布慢慢演变到一个平衡分布。有趣的是,这种分布产生了一个瞬态化学势,表明数量变化过程比弹性过程慢得多。

英文摘要:

In a previous work [arXiv:1009.4363], we have studied the evolution of a scalar field with a quartic coupling, driven by a classical source that initializes it to a non-perturbatively large value. At leading order in the coupling, the evolution of this system is given by classical solutions of the field equation of motion. However, this system is subject to a parametric resonance that leads to secular divergences in higher order corrections to physical observables. We have proposed a scheme that resums all the leading secular terms: this resummation leads to finite results at all times, and we have observed also that it makes the pressure tensor of the system relax to its equilibrium value. In the present paper, we continue the study of this system by looking at finer details of its dynamics. We first compute its spectral function at various stages of the evolution, and we observe that after a fairly short transient time there are well defined massive quasi-particles. We then consider the time evolution of the momentum distribution of these quasi-particles, and we show that after a stage dominated by the parametric resonance, this distribution slowly evolves to an equilibrium distribution. Interestingly, this distribution develops a transient chemical potential, signalling the fact that number changing processes are much slower than the elastic ones.

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