RII Track-4:NSF: Exploring the Emergent Features of Exotic Nuclear Systems with First-principles Theory of Nuclear Reactions

这项研究项目旨在通过核反应的第一性原理计算来研究原子核的基本性质及其在宇宙中的作用。最近在我们对核力的理解上的进步开启了以原子核为重点的第一性原理研究的时代。然而，利用这些进展来研究涉及比最轻的同位素更重的元素的核反应的现有方法仍然依赖于近似，从而引入了重大的不确定性。为了填补这一空白，该项目将利用美国最先进的超级计算机提供的最先进的数学技术和计算资源。通过这样做，它的目标是在描述核反应方面达到前所未有的准确水平。这一努力预计将对目前实验方法无法实现的系统产生高度准确的预测，从而潜在地催化核科学和天体物理方面的突破。该项目最终将开发一种新的计算工具，能够在统一的框架内研究各种反应过程。预期的结果不仅将在核物理领域产生重大影响，而且将在天体物理研究的各个领域以及国家安全的背景下产生重大影响。最近，我们对核力和高性能计算的理解取得进展，为核物理的第一原理计算时代铺平了道路。这些进展为轻核带来了前所未有的准确结果。然而，即使在最先进的计算平台上，对于超过12个粒子的系统，这种计算很快就变得不可行。在这方面，已经证明，在新的基础上重新表述多体问题--利用核物理史上早些时候确定的近乎完美的对称性--可以减轻第一原理计算固有的组合挑战。这种创新的方法，即对称性适应的无核壳模型，使得能够从头开始描述包含多达40个粒子的系统的核结构，实现了对实验数据的高保真，特别是对于传统上很难在从头方法中把握的电磁跃迁。在这一成功的基础上，目前的项目旨在通过利用共振群方法(RGM)将这一理论框架扩展到包括核反应。该项目与劳伦斯利弗莫尔国家实验室合作，寻求扩大从头算反应计算的范围，以研究直到钙区的原子核。在RGM框架内，该项目将允许从第一性原理对涉及各种质量分配和轻射弹的反应过程进行耦合通道描述。预期的结果有望在天体物理学的多个领域产生影响，并对国家安全产生重大影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This research project aims to investigate the fundamental properties of the atomic nucleus and its role in the cosmos through first-principles calculations of nuclear reactions. Recent advancements in our understanding of the nuclear force have ushered in an era of first-principles studies focusing on atomic nuclei. However, existing approaches utilizing these advancements for the study of nuclear reactions involving elements heavier than the lightest isotopes still rely on approximations, thereby introducing significant uncertainties. To address this void, the project will leverage state-of-the-art mathematical techniques and computational resources from the most advanced supercomputers in the US. By doing so, it aims to achieve unprecedented levels of accuracy in the description of nuclear reactions. This endeavor is expected to yield highly accurate predictions for systems currently beyond the reach of experimental methodologies, thereby potentially catalyzing breakthroughs in both nuclear science and astrophysics. The project will culminate in the development of a novel computational tool capable of investigating various reaction processes within a unified framework. The anticipated outcomes are poised to exert a significant impact not only in the domain of nuclear physics but also across various fields of astrophysical research as well as in the context of national security.Recent advancements in our comprehension of the nuclear force and high-performance computing, have paved the way for the era of first-principles calculations in nuclear physics. These developments have yielded unprecedentedly accurate results for light nuclei. However, such calculations rapidly become computationally infeasible for systems exceeding a dozen particles, even on the most advanced computing platforms. In this context, it has been demonstrated that reformulating the many-body problem in a new basis—capitalizing on nearly perfect symmetries identified earlier in the history of nuclear physics—can mitigate the combinatorial challenges inherent to first-principles calculations. This innovative approach, the Symmetry-adapted No Core Shell Model has enabled the ab initio description of nuclear structures for systems containing up to 40 particles, achieving a high fidelity to experimental data, particularly for electromagnetic transitions traditionally difficult to grasp in ab initio approaches. Building on this success, the current project aims to extend this theoretical framework to encompass nuclear reactions by utilizing the Resonating Group Method (RGM). In collaboration with Lawrence Livermore National Laboratory, the project seeks to expand the reach of ab initio reaction calculations to study nuclei up to the calcium region. Within the RGM framework, the project will allow a coupled-channel description of reaction process involving various mass partitions and light projectiles from first-principles. The anticipated outcomes hold the promise of impactful applications across multiple domains of astrophysics, as well as significant implications for national security.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.