Pairing in exotic neutron rich nuclei around the drip line and in the crust of neutron stars

TL;DR

This paper investigates neutron pairing in exotic neutron-rich nuclei near the drip line and in neutron star crusts, using advanced density-functional methods to understand pairing behavior and the impact of shell effects and continuum resonances.

Contribution

It provides a systematic comparison of pairing properties using different theoretical models and pairing interactions, highlighting the persistence of pairing at the drip line due to continuum effects.

Findings

Neutron pairing decreases towards the drip line but is influenced by shell effects.

Resonances in the continuum can sustain pairing even at the drip line.

Differences between HFB and BCS approaches can be significant in these systems.

Abstract

Exotic and drip-line nuclei as well as nuclei immersed in a low density gas of neutrons in the outer crust of neutron stars are systematically investigated with respect to their neutron pairing properties. This is done using Skyrme density-functional and different pairing forces such as a density-dependent contact interaction and a separable form of a finite-range Gogny interaction. Hartree-Fock-Bogoliubov and BCS theories are compared. It is found that neutron pairing is reduced towards the drip line while overcast by strong shell effects. Furthermore resonances in the continuum can have an important effect counterbalancing the tendency of reduction and leading to a persistence of pairing at the drip line. It is also shown that in these systems the difference between HFB and BCS approaches can be qualitatively large.