A theoretical investigation of few-body systems

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。少数几体碰撞在超冷量子气体实验中发挥着越来越重要的作用。这项工作解决了关于这种碰撞的一些最重要的悬而未决的问题：当三个物体在光学晶格的降维中碰撞时会发生什么？当四个物体相撞时会发生什么？如果有的话，埃菲莫夫物理学在这些碰撞中扮演的角色是什么？最近的理论进展表明，Efimov物理是大多数超冷三体碰撞的基础，决定了相关的弹性和非弹性速率系数与能量、质量和散射长度的关系。将这一认识扩展到回答这些悬而未决的问题是这项工作的重点。考虑到少体碰撞在超冷实验中的重要性，获得更完整的理论理解是必不可少的。理论输入既有助于设计更好的实验，也有助于解释已测量的结果。光学晶格中的超冷实验--因此在降维中--对于超冷原子物理的潜在技术应用变得特别重要。通过与实验者互动并回答对他们重要的问题，这项工作因此可以推动超古物理学的更广泛努力。更广泛地说，少体物理学是原子物理学、化学物理学和核物理学的交集。例如，三体复合过程，即三个自由原子碰撞形成双原子分子，是由原子形成分子的最简单的反应之一。因此，它们在星际云和行星大气的化学中扮演着重要的角色。在更高的温度下，这些反应对燃烧也变得重要。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Few-body collisions are playing an increasingly important role in experiments on ultracold quantum gases. This work addresses some of the most important outstanding questions about such collisions: What happens when three bodies collide in the reduced dimensions of an optical lattice? What happens when four bodies collide? What, if any, is the role of Efimov physics in these collisions? Recent theoretical progress suggests that Efimov physics underlies most ultracold three-body collisions, determining the dependence of the associated elastic and inelastic rate coefficients on energy, mass, and scattering length. Extending this understanding to answer these open questions is the focus of this work. Given the importance of few-body collisions in ultracold experiments, gaining a more complete theoretical understanding is essential. Theoretical input can help both in the design of better experiments and in interpreting what has been measured. Ultracold experiments in optical lattices - and thus in reduced dimensions - are becoming especially important for potential technological applications of ultracold atom physics. By interacting with experimentalists and answering the questions important for them, this work can thus advance the broader efforts in ultracold physics. Even more broadly, few-body physics lies at the overlap of atomic, chemical, and nuclear physics. For instance, the process of three-body recombination, where three free atoms collide to form a diatomic molecule, is one of the simplest reactions that forms molecules from atoms. They thus play an important role in the chemistry of interstellar clouds and planetary atmospheres. At higher temperatures, these reactions also become important for combustion.