New Directions in Nuclear Structure Theory

研究项目：物理学领域的一个基本的突出问题是从中子和质子（统称为核子）之间的基本相互作用出发，仅采用量子力学多体理论来理解原子核的结构和性质。 近十年来，由于核多体理论的新发展和计算机技术的进步，这一问题的解决取得了很大进展。 这些发展之一是所谓的无核壳模型（NCSM），其中一个核中的所有核子都被视为活跃的，而不是只有几个价核子在假定的惰性核之外。 NCSM方法简化了要解决的多体问题的结构，并且在描述轻核的性质方面取得了相当大的成功，直到接近氧的质量，即，16号核子。 同样的NCSM方法可以并且现在正在应用于核反应理论。 从这些研究中得出的一个基本进展是，不仅理解了核子之间的成对相互作用在确定核结构中的重要性，而且理解了三重态（或三核子）相互作用的重要性。 需要做更多的工作来确定四核子和更高核子的相互作用是否也是必要的。 另一个重要的问题是理解双核子系统所需的能量相对于一个核中所有核子可获得的能量之间的关系。更广泛的影响：我们的NCSM方法不仅在理论核物理中有广泛的应用，而且在原子和分子物理以及凝聚态物理中，例如，少数费米子的问题，例如，被谐振子陷阱束缚的电子。 此外，我们的研究计划正在积极教育和指导新一代年轻的核理论家。 例如，在上一个奖项期间，我们的研究小组包括两名本科生，两名研究生和三名博士后研究助理。 首席研究员还在亚利桑那大学教授本科生和研究生核物理课程，并在国际暑期学校、讲习班和研讨会上讲授核结构理论。

Research Program: One of the fundamental outstanding problems in the field of physics is to understand the structure and properties of the atomic nucleus starting from the basic interactions among the neutrons and protons (collectively called nucleons) and employing only quantum mechanical many-body theory. Great progress has been made in solving this problem in the last ten years due to new developments in nuclear many-body theory and advances in computer technology. One of these developments is the so-called No Core Shell Model (NCSM), in which all the nucleons in a nucleus are treated as being active, instead of only a few valence nucleons outside an assumed inert core. The NCSM approach simplifies the structure of the many-body problem to be solved and has had considerable success in describing the properties of light nuclei, up to masses near oxygen, i.e., nucleon number 16. This same NCSM approach can be and is being now applied to nuclear reaction theory. One of the fundamental advances following from these investigations is the understanding of the importance of not only pair-wise interactions among nucleons in determining nuclear structure, but also of triplet (or three-nucleon) interactions. More work needs to be done to determine whether or not four-nucleon and higher-nucleon interactions are also necessary. Another important problem is to understand the relationship between the energy required in the two-nucleon system relative to the energy available for all the nucleons in a nucleus.Broader Impact: Our NCSM approach not only has wide applications in theoretical nuclear physics but also in atomic and molecular physics and in condensed matter physics, such as, the problem of a small number of fermions, e.g., electrons, constrained by an harmonic oscillator trap. In addition, our research program is actively educating and mentoring a new generation of young nuclear theorists. For example, during the previous award period, our research group included two undergraduate students, two graduate students, and three post-doctoral research associates. The principal investigator also teaches undergraduate and graduate nuclear physics courses at the University of Arizona and lectures on nuclear structure theory at international summer schools, workshops and symposia.