纵向膨胀不稳定性的非线性放大
Nonlinear amplification of instabilities with longitudinal expansion
摘要：
我们研究各向异性膨胀系统中的非平衡不稳定性动力学。这种系统最突出的例子是相对论性重离子碰撞实验中的“膨胀”，其中膨胀是近似助推不变初始条件的结果。在这里，我们考虑的问题的参数共振的标量$N$分量量子场论与助推不变的初始条件，这是类似的精神。我们发现，动力学的许多方面可以通过引入广义共形时间来解析地处理。初级不稳定性，这是由线性化的演化方程描述，被认为是导致一个二级制度的扩增与强烈增强的增长率，由于非线性校正。对于二次不稳定性，我们提出了一个弱耦合的幂次计算方案，并讨论了它们对各向同性问题和建立状态方程的作用。
英文摘要：
We study the dynamics of nonequilibrium instabilities in anisotropically expanding systems. The most prominent example of such a system is the 'Glasma' in the context of relativistic heavy-ion collision experiments, where the expansion is a consequence of approximately boost-invariant initial conditions. Here we consider the problem of parametric resonance in scalar $N$-component quantum field theories with boost-invariant initial conditions, which is similar in spirit. We find that many aspects of the dynamics can be treated analytically by introducing a generalized conformal time. Primary instabilities, which are described by the linearized evolution equations, are seen to lead to a secondary regime of amplifications with strongly enhanced growth rates due to nonlinear corrections. For the secondary instabilities we present a power-counting scheme for weak coupling, and discuss their role for the question of isotropization and the establishment of an equation of state.
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