Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. XI: Stabilizing neutron stars against a ferromagnetic collapse

TL;DR

This paper introduces the HFB-18 mass model with a modified Skyrme force that prevents ferromagnetic collapse in neutron stars while maintaining high accuracy in nuclear mass predictions.

Contribution

The authors develop a new HFB mass model with density-dependent force terms that stabilize neutron stars against ferromagnetic collapse, improving upon previous models.

Findings

Achieves an rms deviation of 0.585 MeV in mass predictions.

Successfully avoids high-density ferromagnetic instability in neutron stars.

Maintains similar mass fit accuracy as previous models.

Abstract

We construct a new Hartree-Fock-Bogoliubov (HFB) mass model, labeled HFB-18, with a generalized Skyrme force. The additional terms that we have introduced into the force are density-dependent generalizations of the usual $t_1$ and $t_2$ terms, and are chosen in such a way as to avoid the high-density ferromagnetic instability of neutron stars that is a general feature of conventional Skyrme forces, and in particular of the Skyrme forces underlying all the HFB mass models that we have developed in the past. The remaining parameters of the model are then fitted to essentially all the available mass data, an rms deviation $\sigma$ of 0.585 MeV being obtained. The new model thus gives almost as good a mass fit as our best-fit model HFB-17 ($\sigma$ = 0.581 MeV), and has the advantage of avoiding the ferromagnetic collapse of neutron stars.