Coordination Funds

统计物理学中一个长期存在且令人着迷的问题，旨在理解基于宏观参数的平衡物理学如何从经典或量子系统的微观动力学中出现。对于封闭量子系统，这个问题获得了一个额外的扭曲，因为描述量子混沌和不可逆性的形式主义仍在进行研究。量子模拟器的出现，最值得注意的是，相互作用的超冷原子，导致了这方面研究活动和开创性实验的异常增加。在理论方面，在相互作用的多体系统中有强有力的证据和遍历动力学的标准，而多体局部化已经成为热化的一个潜在例外。作为一种中间行为，具有约束动力学的系统是人们关注的焦点。我们倡议的目标是连接这三个支柱的非平衡系统-遍遍性，多体定位，和约束动力学。特别是，我们将设计并开展超冷原子实验，定性和定量地解决和澄清有关热化时间尺度，流体力学的出现，多体局域相的存在和相应跃迁的表征等开放关键问题，最值得注意的是，实现和研究几个约束动力学实例。关于约束动力学，我们将研究hilbert空间碎片化、分形系统、动力学约束模型和格规理论中的非平衡动力学。我们将确定实验装置和合适的观测对象，以利用超冷原子气体的能力详细研究这些慢动力学实例。我们的实验包括玻色子量子气体显微镜，将实现格规理论的费米子Yb实验，以及具有极端质量不平衡的重-轻混合物。我们的理论方法结合了最先进的计算方法，具有约束动力学和多体定位的系统理论，分析方法，量子光学和统计物理。我们期望在这个研究单元中非常密切的实验理论合作将导致新的结果，预计将大大促进对非平衡动力学的理解。从长远来看，我们的研究将对控制热化和非遍历性的概念产生影响，以设计具有新性质和功能的人工量子物质。

A long-standing and fascinating question from statistical physics aims at understanding how equilibrium physics —based on macroscopic parameters— emerges from the microscopic dynamics of classical or quantum systems. For closed quantum systems, this question acquires an additional twist since the formalism to describe quantum chaos and irreversibility is still subject to ongoing research. The advent of quantum simulators, most notably, interacting ultracold atoms, has led to an exceptional increase in research activity and groundbreaking experiments in this context. On the theory side, there are strong evidence and criteria for ergodic dynamics in interacting many-body systems, while many-body localization has emerged as a potential exception from thermalization. As an intermediate behavior, systems with constrained dynamics are of central interest. The goal of our initiative is to connect these three pillars of nonequilibrium systems—ergodicity, many-body localization, and constrained dynamics. In particular, we will devise and carry out ultracold atom experiments that qualitatively and quantitatively serve to address and clarify open key questions concerning thermalization time scales, the emergence of hydrodynamics, the existence of many-body localized phases and the characterization of the corresponding transition, and most notably, the realization and study of several instances of constrained dynamics. Concerning constrained dynamics, we will investigate Hilbert-space fragmentation, fractonic systems, kinetically constrained models, and nonequilibrium dynamics in lattice-gauge theories. We will identify experimental setups and suitable observables to study these instances of slow dynamics in detail using the capabilities of ultracold atomic gases. Our experiments include bosonic quantum-gas microsocopes, a fermionic Yb experiment that will realize a lattice-gauge theory, and a heavy-light mixture with an extreme mass imbalance. Our theoretical approaches combine state-of-the-art computational methods, the theory of systems with constrained dynamics and many-body localization, analytical methods, quantum optics, and statistical physics. We expect that the very close experiment theory collaborations in this research unit will lead to novel results that are expected to substantially advance the understanding of nonequilibrium dynamics. As a long-term perspective, our research will have an impact on concepts for controlling thermalization and non-ergodicity to design artificial quantum matter with new properties and functionalities.