A Novel Many-Body Method for the Description of Open-Shell Nuclei From First Principles

这个项目试图找到核理论中一些关键问题的答案：亚原子物质是如何组织自己的，出现了什么模式？控制物质结构的基本相互作用被理解了吗？这是推动核物理领域未来几年研究努力的两个主要问题。对奇异的富含中子的原子核的实验推动已经迫使我们修改了对核物理的理解，像FRIB这样的设施，稀有同位素光束设施，将提供丰富的同位素新数据，这些数据以前无法在实验室条件下研究。在这些核中，结构变化是由核力、连续体和强多体相关性的复杂相互作用驱动的，这标志着传统的核结构单参考模型的崩溃。这具有深远的意义，例如，对天体物理过程中关键原子核的半衰期，或核存在的极限，解释了为什么O-24而不是O-28是自然界中发现的最重的氧同位素。顾名思义，PI开发的多参考介质相似性重整化群（mrim - srg）是一种新颖的多体方法，可以应用于基于单参考的描述不再是合适起点的核（或其他多体系统）。根据目前的合同，MR-IM-SRG将扩展到计算中质量和重开壳核的激发态性质，包括电磁和弱跃迁速率。利用最先进的相互作用和手性有效场论（EFT）的电流，PI和他的学生将研究所谓的幻数的侵蚀和出现，计算与核天体物理学相关的质量和衰变率，并研究中子表皮的形成等影响，这些影响限制了核状态方程。MR-IM-SRG的系统性改进和手性EFT的输入将使我们能够控制和量化这些结果的理论不确定性。这些努力将有助于通过与实验数据的对抗来识别理论框架中的潜在问题，并指导国家超导回旋加速器实验室（NSCL）和FRIB以及全球其他设施的实验工作。该项目将为一名研究生提供部分支持，该研究生将参与核物理前沿的研究，并接受高性能计算方面的培训。

This project seeks to find answers to a number of key questions in nuclear theory: How does subatomic matter organize itself, and what patterns emerge? Are the fundamental interactions that govern the structure of matter understood? These are two of the major questions that drive the research efforts in the field of nuclear physics in years to come. The experimental push towards exotic neutron-rich nuclei has already forced us to revise our understanding of nuclear physics, and facilities like FRIB, the Facility for Rare Isotope Beams, will provide a wealth of new data from isotopes that could not be studied under laboratory conditions before. In these nuclei, structural changes are driven by a complex interplay of nuclear forces, the continuum, and strong many-body correlations which signal the breakdown of traditional single-reference models of nuclear structure. This has far-reaching implications, e.g., on the half lives of key nuclei for astrophysical processes, or the limits of nuclear existence, explaining why O-24 rather than O-28 is the heaviest oxygen isotope found in nature. As its name suggests, the Multi-Reference In-Medium Similarity Renormalization Group MR-IM-SRG) developed by the PI is a novel many-body method that can be applied to nuclei (or other many-body systems) for which single-reference based descriptions are no longer an appropriate starting point. Under the current award, the MR-IM-SRG will be extended to the computation of excited state properties in medium-mass and heavy open-shell nuclei, including electromagnetic and weak transition rates. Using state-of-the-art interactions and currents from Chiral Effective Field Theory (EFT) the PI and his students will investigate the erosion and emergence of the so-called magic numbers, compute masses and decay rates relevant for nuclear astrophysics, and study effects like the formation of neutron skins that constrain the nuclear equation of state. The systematic improvability of the MR-IM-SRG and the inputs from Chiral EFT will allows us to control and quantify the theoretical uncertainties of these results. These efforts will help to identify potential issues in the theoretical framework through the confrontation with experimental data, and guide experimental efforts at the National Superconducting Cyclotron Laboratory (NSCL) and FRIB, as well as other facilities worldwide. The project will provide partial support for one graduate student, who will participate in research at the forefront of nuclear physics, and receive training in high-performance computing.