Ab initio theory for major questions in subatomic physics

也许是宇宙中最复杂的量子系统，原子核的许多方面与自然界中一些最深刻的问题交织在一起。长期以来被认为是一门现象学学科，现代核理论现在的目标是从头开始面对这些问题：作为一门能够提供具有量化不确定性的可靠预测的第一原理学科。要做到这一点，我们必须首先对把质子和中子束缚成原子核的力作出一致的描述，并提出仅从这些相互作用出发解决核多体问题的方法。******我之前的发现基金对于建立价空间中相似性重整化群（VS-IMSRG）作为一个强大的从头开始多体工具至关重要。由于具有大空间方法的准确性，但壳层模型的通用性，VS-IMSRG目前在计算质量为100的区域内所有原子核的所有性质方面的能力是独一无二的。这项发现基金的中心重点将是大力推动提高准确性，估计模型不确定性，并扩大物理范围，以迅速利用这一进展。有了足够的支持，我们将直接为理解加拿大亚原子物理学长期计划中列出的七个“亚原子物理学大问题”中的五个做出贡献。****** VS-IMSRG的范围很广，应用于奇异核提供了一些最令人兴奋的可能性，以了解核的结构如何从核力中产生。我们将在整个图表中讨论主要的核结构问题，例如在轻质量和中等质量区域中原子核（质子和中子流）存在的极限。此外，我们将预测在未开发区域的新幻数的演变，以指导未来的实验工作。从长远来看，我们将为r过程核合成模拟提供第一性原理数据，模拟宇宙中重元素的形成。******此外，我们将讨论与核弱物理有关的一些最重要的问题。其中最突出的是无中微子双β衰变的核矩阵元素，这是从潜在的实验发现中提取绝对中微子质量尺度所必需的。目前正在对轻候选的48Ca、76Ge和82Se进行从头计算，并将达到130Te和136Xe。同样，为了理解暗物质的本质，wimp -原子核的横截面也需要用来解释大规模直接探测搜索的结果。我们将提供wimp -原子核弹性散射结构因子的首次从头计算，其中轻候选粒子的计算正在进行中，并将扩展到129,131Xe。最后，为了理解电弱尺度下的物理，我们将提供从头算输入来提取Gv和CKM夸克混合矩阵的上下分量。

Perhaps the most complicated quantum systems in the universe, the many facets of atomic nuclei are intertwined with some of the most profound questions in nature. Long considered a phenomenological discipline, modern nuclear theory now aims to confront these questions from the ground up: as a first-principles discipline capable of providing reliable predictions with quantified uncertainties. To do this we must first develop a consistent description of the forces which bind protons and neutrons into nuclei, as well as methods which solve the nuclear many-body problem starting only from those interactions.******My previous Discovery Grant was crucial for establishing the valence-space in-medium similarity renormalization group (VS-IMSRG) as a powerful ab initio many-body tool. With the accuracy of large-space methods, but the versatility of the shell model, the VS-IMSRG is currently unique in its capability to calculate essentially all properties of all nuclei up to the mass 100 region. The central focus of this Discovery Grant will be a strong push to improve accuracy, estimate model uncertainty, and expand the physics reach to capitalize quickly on this progress. With sufficient support we will contribute directly to understanding five of the seven "Big Questions in Subatomic Physics", as laid out in the Canadian Subatomic Physics Long Range Plan.******The range of the VS-IMSRG is broad, and applications to exotic nuclei present some of the most exciting possibilities to understand how the structure of nuclei emerges from nuclear forces. We will address major nuclear structure issues across the chart such as the limits of existence of nuclei (the proton and neutron driplines) in the light and medium-mass regions. Furthermore, we will predict the evolution of new magic numbers in unexplored regions to guide future experimental efforts. In the long term we will contribute first-principles data for r-process nucleosynthesis simulations modeling the formation of heavy elements in the universe.******In addition we will address some of the most important questions related to nuclear-weak physics. The most prominent of these is the nuclear matrix element for neutrinoless double beta decay, which is necessary to extract the absolute neutrino mass scale from a potential experimental discovery. Ab initio calculations are underway for the light candidates 48Ca 76Ge and 82Se and will reach 130Te and 136Xe. Similarly for understanding the nature of dark matter, WIMP-nucleus cross sections are needed to interpret results of large-scale direct-detection searches. We will provide the first ab initio calculations of WIMP-nucleus elastic-scattering structure factors, where calculations for light candidates are underway, and will be extended to 129,131Xe. Finally for understanding physics at the electroweak scale, we will provide ab initio input to extract Gv and the up-down component of the CKM quark-mixing matrix.