发表机构
Institut für Theoretische Physik, Universität Heidelberg; Department of Physics and Astronomy, Ghent University; Institute of Theoretical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University（海德堡大学理论物理研究所; 根特大学物理与天文学系; 雅盖隆大学理论物理研究所与马克·卡克复杂系统研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文综述流体动力学吸引子概念，区分吸引子化与流体动力学化，比较多种理论框架，并探讨其在核碰撞和超冷原子气体中的应用。
AI 中文摘要
吸引子是在选定的一组可观测量中定义的有效低维结构，来自不同初始状态的轨迹会趋近于这些结构；流体动力学吸引子是指那些晚期演化由流体动力学本构关系支配的吸引子。受核碰撞和超冷原子气体的启发，本章区分了吸引子化（对初始状态空间中某些方向敏感性的丧失）与流体动力学化（流体动力学本构关系有效性的开始）。我们主要利用共形、boost不变的Bjorken流，比较了Müller-Israel-Stewart型理论、动力学理论、全息方法和经典Yang-Mills场。由非流体动力学模式衰变产生的前向吸引，与能够选择唯一正则解的回拉吸引，以及能够在微观弛豫之前抑制初始状态敏感性（无论随后是否出现流体动力学状态）的膨胀驱动吸引相区分。发散梯度展开及其transseries完备化、状态空间图像和绝热流体动力学化提供了互补的描述。对核碰撞的应用包括粒子产生、横向能量和流、吸引背景周围的初始化和线性响应、喷注淬灭以及受吸引子启发的流体动力学模型修正。对于超冷费米气体，我们回顾了散射长度驱动下体通道吸引子的理论提议，并将其与近期短时接触和动量分布动力学的测量区分开来。
英文摘要
Attractors are effective low-dimensional structures, defined in a chosen set of observables, that trajectories from different initial states approach; hydrodynamic attractors are those on which the late-time evolution is governed by hydrodynamic constitutive relations. Motivated by nuclear collisions and ultracold atomic gases, this chapter distinguishes attractorization (the loss of sensitivity to some directions in the space of initial states) from hydrodynamization (the onset of validity of hydrodynamic constitutive relations). Using mainly conformal, boost-invariant Bjorken flow, we compare Müller-Israel-Stewart-type theories, kinetic theory, holography, and classical Yang-Mills fields. Forward attraction, produced by the decay of non-hydrodynamic modes, is distinguished from pullback attraction, which can select a unique regular solution, and from expansion-driven attraction, which can suppress initial-state sensitivity before microscopic relaxation, with or without a subsequent fluid regime. Divergent gradient expansions and their transseries completions, the state-space picture, and adiabatic hydrodynamization provide complementary descriptions. Applications to nuclear collisions include particle production, transverse energy and flow, the initialization of and linear response around attracting backgrounds, jet quenching, and attractor-informed modifications of hydrodynamic models. For ultracold Fermi gases, we review theoretical proposals for bulk-channel attractors under scattering-length drives and distinguish them from recent measurements of short-time contact and momentum-distribution dynamics.
Comments57 pages, 11 figures. Invited chapter for Encyclopedia of Nuclear Physics. Comments welcome!
