标题： 子空间投影多参考协变密度泛函理论 显示英文标题

标题： Subspace-projected multireference covariant density functional theory

摘要： 多参考密度泛函理论（MR-DFT）一直是研究原子核低激发态和无中微子双贝塔衰变（$0\nu\beta\beta$）的关键方法。然而，由于计算需求，量化其理论不确定性一直是一个重大挑战。本研究引入了一种子空间投影协变密度泛函理论（SP-CDFT），该方法能够高效模拟原子核低激发态的MR-CDFT计算。这种方法结合了特征向量延拓法与基于相对论能量密度泛函（EDF）的量子数投影生成坐标法。我们应用SP-CDFT研究了核物质物理量、核低激发谱以及两个最重候选核的$0\nu\beta\beta$衰变的核矩阵元（NMEs）之间的关联。我们的研究结果显示，$0\nu\beta\beta$衰变的NMEs与$2_1^+$态的激发能以及$E2$转换强度之间通常存在较强的关联，尽管这种关联在不同核之间变化显著。此外，这项工作也为利用光谱数据改进核EDF参数奠定了基础。 显示英文摘要

摘要： Multireference density functional theory (MR-DFT) has been a pivotal method for studying nuclear low-lying states and neutrinoless double-beta ($0\nu\beta\beta$) decay. However, quantifying their theoretical uncertainties has been a significant challenge due to the computational demands. This study introduces a subspace-projected covariant density functional theory (SP-CDFT), which efficiently emulates MR-CDFT calculations for nuclear low-lying states. This approach leverages the eigenvector continuation method combined with the quantum-number projected generator coordinate method, based on a relativistic energy density functional (EDF). We apply SP-CDFT to investigate the correlations among the physical quantities of nuclear matter, nuclear low-lying spectroscopy, and the nuclear matrix elements (NMEs) of $0\nu\beta\beta$ decay in the two heaviest candidate nuclei. Our findings reveal generally strong correlations between the NMEs of $0\nu\beta\beta$ decay and the excitation energy of the $2_1^+$ state, as well as the $E2$ transition strength, although these correlations vary significantly among nuclei. This work also paves the way for refining nuclear EDF parameters using spectroscopic data.