New Tools to Study Strong Interaction Physics

公认的强核力理论——量子色动力学（QCD, Quantum Chromodynamics）——将原子核凝聚在一起已经有35年的历史了，但使用起来非常困难，而且在它最突出的领域，人们对它的理解也很差；例如，我们知道质子和中子（统称为“核子”）是由被称为夸克和胶子的更小的成分组成的，但它们究竟是如何组装成核子的，我们充其量也不清楚。在这项资助中，Belitsky和Lebed将使用各种高性能的数学工具，通常是从弦理论中借来的，来在这个复杂的领域取得进展。Belitsky是广义部分子分布理论方面的专家，广义部分子分布是核子最精确定义的观测值，而Lebed是大型Nc QCD方面的专家，在这种情况下，通过增加更多的自由度，求解QCD变得比自然界中更容易，这是矛盾的。此外，Belitsky已经熟练掌握了一种叫做可积性的强大技术，在这种技术中，QCD和类似的理论可以在数学上与铁磁体和其他“自旋链”等系统的物理联系起来。与此同时，Lebed正在研究“全息QCD”，这是基于弦理论的一个想法，即QCD和相关的强相互作用理论可以与弯曲空间上的弱相互作用引力有关。Belitsky和Lebed各自将在这些项目领域指导一名博士生。

The accepted theory of the strong nuclear force that holds atomic nuclei together, called QCD (Quantum Chromodynamics) has been known for 35 years, but is extraordinarily difficult to use and is poorly understood in precisely the regions where it is most prominent; for example, we know that protons and neutrons (collectively, "nucleons") are made of smaller constituents named quarks and gluons, but exactly how they are assembled into nucleons remains murky at best. In this grant, Belitsky and Lebed will use a variety of high-powered mathematical tools, often ones borrowed from string theory, to make headway in this complicated landscape. Belitsky is an expert in the theory of generalized parton distributions, which are the most precisely defined observables possible for nucleons, while Lebed is an expert on large Nc QCD, in which solving QCD becomes paradoxically simpler to solve by adding more degrees of freedom than occur in nature. In addition, Belitsky has become adept in a powerful technique called integrability, in which QCD and similar theories can be mathematically related to the physics of systems like ferromagnets and other "spin-chains". Meanwhile, Lebed is studying "holographic QCD," which is based upon an idea from string theory, that QCD and related strongly-interacting theories can be related to weakly-interacting gravity on a curved space. Each of Belitsky and Lebed will mentor a Ph.D. student in these project areas.