Analytic structure of nonhydrodynamic modes in kinetic theory
Analytic structure of nonhydrodynamic modes in kinetic theory
复制标题
动力学理论中非流体动力模态的解析结构
DOI：
10.1140/epjc/s10052-019-7271-9
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
U. Wiedemann
中科院分区：
文献类型：
--
作者：
A. Kurkela;U. Wiedemann
物理系统如何接近流体动力学行为取决于非流体动力学模式的衰减。在这里，我们开始从相对论动力学理论，编码松弛机制由不同的时间尺度，从而共享一般弱耦合非平衡系统的基本特征。通过解析求解的延迟相关函数，我们澄清了如何产生一般的分支削减从非集体粒子激发，他们如何与集体流体动力学激发所产生的极点接口，以及在何种程度上的外观极点仍然是最好的一个模糊的签名流体动力学行为的发病。我们观察到，比流体动力学弛豫时间尺度慢的过程可以使已经达到流体动力学行为的系统在后期脱离流体动力学。此外，对该模型的分析控制使我们能够显式地演示如何恢复相关函数的流体动力梯度展开，以便恢复相关函数的完整且精确的非分析形式。
How physical systems approach hydrodynamic behavior is governed by the decay of nonhydrodynamic modes. Here, we start from a relativistic kinetic theory that encodes relaxation mechanisms governed by different timescales thus sharing essential features of generic weakly coupled nonequilibrium systems. By analytically solving for the retarded correlation functions, we clarify how branch cuts arise generically from noncollective particle excitations, how they interface with poles arising from collective hydrodynamic excitations, and to what extent the appearance of poles remains at best an ambiguous signature for the onset of fluid dynamic behavior. We observe that processes that are slower than the hydrodynamic relaxation timescale can make a system that has already reached fluid dynamic behavior to fall out of hydrodynamics at late times. In addition, the analytical control over this model allows us to explicitly demonstrate how the hydrodynamic gradient expansion of the correlation function can be resummed such that the complete and exact non-analytic form of the correlation function can be recovered.