Global sensitivity analysis and uncertainty quantification of nuclear low-lying states and double-beta decay with a covariant energy density functional

We present a statistical analysis of nuclear low-lying states within the framework of multireference covariant density functional theory (MR-CDFT) using a relativistic point-coupling energy density functional (EDF). This study is made possible by the newly developed subspace-projected (SP) -CDFT, where the wave functions of nuclear low-lying states for target EDF parameter sets are expanded in a subspace spanned by the wave functions of low-lying states from training parameter sets. We analyze the global sensitivity of excitation energies, electric quadrupole transition strengths, and the nuclear matrix element of neutrinoless double-beta decay in ^136Xe and ^150Nd to EDF parameters, and explore the correlations between these quantities and nuclear matter properties. Furthermore, we quantify the statistical uncertainty of low-lying states through their posterior distributions.