High-performance algorithm to calculate spin- and parity-dependent nuclear level densities

A new algorithm for calculating the spin- and parity-dependent shell-model nuclear level densities using the moments method in the proton-neutron formalism is presented. A new, parallelized code based on this algorithm was developed and tested using up to 4000 cores for a set of nuclei from the sd-, pf-, and pf+g9/2-model spaces. By comparing the nuclear level densities at low excitation energy for a given nucleus calculated in two model spaces, such as pf and pf+g9/2, one can estimate the ground-state energy in the larger model space, which is not accessible to direct shell-model calculations due to the unmanageable dimension. Examples for the ground-state energies of for Ge64 and Se68 in the pf+g9/2 model space are presented.