Exploring Ultracold Matter Along the Complexity Axis

简单的事物可以联合收割机组合成更复杂的事物，这是一个基本的概念，这种复杂性是我们在自然界中看到的丰富多样的现象的基础。因此，在尽可能多的环境中理解这种丰富性和复杂性对科学的进步至关重要;从许多例子中可以得出关于世界如何运作的复杂性的一般性想法。这个项目依赖于这样一种认识，即像原子这样看似简单的东西可以呈现出令人惊讶的复杂行为。具体来说，在绝对零度以上百万分之一度的温度下保持气态的原子可以高精度地测量，这揭示了令人惊讶的复杂性。例如，原子可以指向某个方向，就像小磁棒一样，这个方向可以影响气体的热力学以及原子之间的相互作用，有时以不可预测的方式改变它们的轨迹。另一方面，原子的相对简单性给我们带来了希望，希望我们能够详细地理解这些复杂性，从真正混乱的部分中挑选出可能具有潜在简单性的部分。因此，这项工作也是了解工程原子的能力和限制，以特定的目的。拟议的工作将详细探讨近年来出现的超冷碰撞的新方面。一个是在镧系元素原子如镝和铒的碰撞中出现了巨大的共振态密度。这种情况可能会导致新的现象，在多体气体和新的见解的混沌行为和孤立系统的再热动力学的另一方面，从而有助于小尺度非平衡动力学。这一发展的一部分试图将信息论的技术应用于复杂分子的结构问题。第二个方面是超冷分子的超共振散射的可能性，其状态密度远高于镧系元素原子。长寿命的碰撞复合物的发生已被经验验证，并测量其寿命。这项工作将试图了解这些不寻常的，四个原子的微滴的属性，使用统计技术。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

It is a fundamental notion that simple things can combine into more complex things, and this complexity underlies the rich variety of phenomena that we see in nature. It is therefore important to the progress of science to understand this richness and complexity in as many environments as possible; from many examples will come general ideas about the intricacies of how the world works. This project relies on the recognition that things as seemingly simple as atoms can present surprisingly complex behavior. Specifically, atoms held in the gaseous state at temperatures one millionth of a degree above absolute zero can be measured with high precision that reveal surprising complexity. For instance, the atoms can be pointed in a certain direction, like little bar magnets, and this direction can influence the thermodynamics of the gas as well as the interactions of the atoms with each other, altering their trajectories in sometimes unpredictable ways. On the other hand, the comparative simplicity of the atoms lends hope that these intricacies can be understood in detail, sorting out the parts that might have an underlying simplicity from those parts that are truly chaotic. This work is therefore also an exercise in understanding the capabilities and limits of engineering atoms to particular purposes.The work proposed will probe in detail new aspects of ultracold collisions that have emerged in recent years. One is the occurrence of an enormous density of resonant states in collisions of lanthanide atoms such as dysprosium and erbium. This circumstance may lead to novel phenomena in many-body gases on the one hand and to new insights into chaotic behavior and dynamics of rethermalization of isolated systems on the other, hence contribute to small-scale nonequilibrium dynamics. Part of this development seeks to bring the techniques of information theory to bear on questions of the structure of complex molecules. A second aspect is the possibility of super-resonant scattering of ultracold molecules, with far higher densities of states than lanthanide atoms. The occurrence of long-lived collision complexes has been empirically verified, and their lifetimes measured. The proposed work will seek to understand the properties of these unusual, four-atom microdroplets, using statistical techniques.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.