Skyrme-Hartree-Fock-Bogoliubov mass models on a 3D Mesh: Effect of triaxial shape

TL;DR

This paper introduces a new Skyrme-EDF-based nuclear mass model that incorporates triaxial deformations using 3D mesh calculations, employing neural networks to optimize parameters efficiently.

Contribution

It presents the first 3D coordinate-space Skyrme-EDF model with triaxial shape considerations, improving mass predictions while managing computational complexity with neural networks.

Findings

Achieved an rms deviation of 741 keV on 2457 nuclear masses.

Successfully modeled charge radii with an rms deviation of 0.024 fm.

Demonstrated the feasibility of including triaxial deformations in large-scale mass models.

Abstract

The modeling of nuclear reactions and radioactive decays in astrophysical or earth-based conditions requires detailed knowledge of the masses of essentially all nuclei. Microscopic mass models based on nuclear energy density functionals (EDFs) can be descriptive and used to provide this information. The concept of intrinsic symmetry breaking is central to the predictive power of EDF approaches, yet is generally not exploited to the utmost by mass models because of the computational demands of adjusting up to about two dozen parameters to thousands of nuclear masses. We report on a first step to bridge the gap between what is presently feasible for studies of individual nuclei and large-scale models: we present a new Skyrme-EDF-based model that was adjusted using a three-dimensional coordinate-space representation, for the first time allowing for both axial and triaxial deformations during the adjustment process. To compensate for the substantial increase in computational cost brought by the latter, we have employed a committee of multilayer neural networks to model the objective function in parameter space and guide us towards the overall best fit. The resulting mass model BSkG1 is computed with the EDF model independently of the neural network. It yields a root mean square (rms) deviation on the 2457 known masses of 741 keV and an rms deviation on the 884 measured charge radii of 0.024 fm.