Microscopic Nuclear Structure Theory

微观核结构理论

• 批准号: 0244389
• 负责人: Bruce Barrett
• 金额: $ 36.3万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0244389&HistoricalAwards=false
• 关键词: Microscopic; Nuclear; Structure; Theory

Tremendous progress has been made in the last ten years in calculating the properties of atomicnuclei microscopically starting with the free nucleon-nucleon (NN) interaction. One of the mostsuccessful theoretical approaches in this regard is the No Core Shell Model(NCSM). Insteadof invoking the standard shell-model assumption, that most of the nucleons occupy an inertcore, one treats all A nucleons as being active. In this way one is able to formulate a systematicprocedure to derive e.ective interactions starting from realistic microscopic ones. This proceduremakes use of the similar structures that two- and three-body clusters are expected to have in allnuclei. It was shown that these e.ective interactions speed up convergence tremendously andmake converged solutions possible.It has now become apparent that present theoretical techniques are able to accurately calculatethe properties of light nuclei using the NN interaction as input. Because the results showa considerable underbinding, it is clear that some extra ingredient is necessary, such as threenucleoninteractions. Hence, the NCSM will be expanded to include the three-body cluster (ore.ective interaction) based not only on the two-body microscopic forces, but also on realisticthree-nucleon (3N) bare interactions. It is important do this, because, for example, the spectraof light nuclei are expected to be sensitive to the spin structure of the 3N interaction. With thesehigher-body interactions one will also be able to perform NCSM calculations for heavier nucleiin smaller basis spaces and obtain better convergence and, hence, more accurate results. Thedevelopment of this three-body cluster approach is an major step forward, as it will enable oneto study the e.ects of current 3N interaction models and models based on chiral perturbationtheory on the spectra. Consequently, it will become an important tool to probe these interactions.By developing a technique for computing the three-body cluster exactly, one can alsoinvestigate its structure, depending upon the number of nucleons in the nuclide being studiedand upon the size of the model space.One of the goals of all nuclear structure calculations is the understanding of collective structuresbased on microscopic calculations. The structure of 12C is an interesting example. The.rst excited 0+ state is believed to have a 3a structure. Converged solutions for this problemare a challenge, but are within the reach of NCSM calculations. Once they can be obtained,one can study in detail the di.erence between the ground state and excited state structures.Another important aspect of the current investigations is the extension of the NCSM methods toarbitary operators. The NCSM is based on a unitary transformation of the cluster Hamiltonian.When one is able to extend this transformation to transition or current operators, it becomespossible to extract meaningful values for physical observables from the NCSM wave functions.The prediction of electroweak properties of light nuclei will be an important application of thisnew technique.

在过去的十年中，在计算自由核定核子（NN）相互作用开始的原子核微小相互作用方面取得了巨大进步。在这方面，最成功的理论方法之一是无核心壳模型（NCSM）。相反，大多数核子占据了肌肉的标准壳模型假设，一个人将所有核子都视为活性。这样，人们就可以制定系统的程序，以从现实的微观相互作用开始。该程序蛋白蛋糕的使用预计在Allnuclei中有望具有两体和三体簇具有的相似结构。结果表明，这些E.1.的相互作用加快了收敛的速度，并且可能会融合解决方案。现在已经显而易见的是，当前的理论技术能够使用NN相互作用作为输入来准确地计算出光核的性质。由于结果大大的固定性，因此很明显，需要一些额外的成分，例如三核互动。因此，NCSM将被扩展到包括基于两体显微力量的三体簇（矿石相互作用），还包括基于逼真的核核（3N）裸露相互作用。重要的是，因为预计光谱对3N相互作用的自旋结构敏感。通过这些高度相互作用，人们还将能够对较重的核素较小的基础空间进行NCSM计算，并获得更好的收敛性，从而获得更准确的结果。这种三体群集方法的开发是向前迈出的重要一步，因为它将能够Oneto研究基于光谱上手性扰动理论的当前3N相互作用模型和模型的e。因此，它将成为探测这些相互作用的重要工具。通过开发一种用于计算三体群集的技术，还可以对其结构进行投资，这取决于对模型空间的核素中的核子数量。 12C的结构是一个有趣的例子。第一个激发0+状态被认为具有3A结构。对于此问题的融合解决方案是一个挑战，但在NCSM计算的范围内。一旦获得了它们，就可以详细研究基态和激发状态结构之间的差异。当前研究的另一个重要方面是NCSM方法的扩展。 NCSM是基于汉密尔顿群集的统一转换。当人们能够将这种转换扩展到过渡或当前运算符时，从NCSM波函数中提取物理可观察物的有意义的值。