Exploring Ultracold Matter Along the Complexity Axis

这是一个基本的概念，简单的东西可以组合成更复杂的东西，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于科学的进步是重要的；从许多例子中将产生关于世界如何运行的错综复杂的一般概念。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，却可以呈现出令人惊讶的复杂行为。具体地说，在绝对零度以上百万分之一度的温度下处于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，有时会以不可预测的方式改变它们的轨迹。另一方面，原子的相对简单性带来了希望，这些错综复杂的部分可以被详细理解，将可能具有潜在简单性的部分与真正混乱的部分区分开来。因此，这项工作也是为了了解工程原子用于特定目的的能力和限度。拟议的工作将详细探索近年来出现的超冷碰撞的新方面。其一是在镝和铒等稀土原子的碰撞中出现了极高密度的共振态。这种情况一方面可能导致多体气体中的新现象，另一方面也可能对孤立系统的混沌行为和再热动力学有新的见解，从而有助于小尺度的非平衡动力学。这一发展的一部分是试图将信息论的技术应用于复杂分子结构的问题。第二个方面是超冷分子的超共振散射的可能性，超冷分子的态密度比稀土原子高得多。长寿命碰撞复合体的存在已经得到了经验验证，并测量了它们的寿命。这项拟议的工作将寻求利用统计技术来了解这些不寻常的四原子微滴的性质。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.