Heavy-ion collisions at BNL’s Relativistic Heavy Ion Collider and CERN’s Large Hadron Collider provide strong evidence for the formation of a quark-gluon plasma, with temperatures extracted from relativistic viscous hydrodynamic simulations shown to be well above the transition temperature from hadron matter. Outstanding problems in QCD include how the strongly correlated quark-gluon matter forms in a heavy-ion collision, its properties off equilibrium, and the thermalization process in the plasma. The theoretical progress in this field in weak-coupling QCD effective field theories and in strong-coupling holographic approaches based on gauge-gravity duality is reviewed. The interdisciplinary connections of different stages of the thermalization process to nonequilibrium dynamics in other systems across energy scales ranging from inflationary cosmology to strong-field QED to ultracold atomic gases are outlined, with emphasis placed on the universal dynamics of nonthermal and hydrodynamic attractors. Measurements in heavy-ion collisions are surveyed that are sensitive to the early nonequilibrium stages of the collision and the potential for future measurements is discussed. The current state of the art in thermalization studies is summarized and promising avenues for further progress are identified.

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QCD 热化：从头算方法和跨学科联系

BNL 的相对论重离子对撞机和欧洲核子研究中心的大型强子对撞机的重离子碰撞为夸克-胶子等离子体的形成提供了强有力的证据，从相对论粘性流体动力学模拟中提取的温度显示远高于强子物质的转变温度。QCD 中的突出问题包括强相关夸克-胶子物质如何在重离子碰撞中形成、其非平衡特性以及等离子体中的热化过程。综述了该领域在弱耦合QCD有效场论和基于规范引力对偶性的强耦合全息方法方面的理论进展。概述了热化过程的不同阶段与其他系统中跨能量尺度的非平衡动力学的跨学科联系，从膨胀宇宙学到强场 QED 再到超冷原子气体，重点放在非热和流体动力学吸引子的普遍动力学上。研究了对碰撞早期非平衡阶段敏感的重离子碰撞测量，并讨论了未来测量的潜力。总结了热化研究的当前技术水平，并确定了进一步进展的有希望的途径。研究了对碰撞早期非平衡阶段敏感的重离子碰撞测量，并讨论了未来测量的潜力。总结了热化研究的当前技术水平，并确定了进一步进展的有希望的途径。研究了对碰撞早期非平衡阶段敏感的重离子碰撞测量，并讨论了未来测量的潜力。总结了热化研究的当前技术水平，并确定了进一步进展的有希望的途径。