Medium polarization and finite size effects on the superfluidity of the inner crust of neutron stars

TL;DR

This paper investigates how medium polarization and finite size effects influence the superfluid pairing gap in the inner crust of neutron stars, revealing significant quenching due to these combined effects.

Contribution

It provides a detailed calculation of the 1S0 pairing gap considering both finite size and medium polarization effects, highlighting their combined impact on superfluidity.

Findings

Both effects significantly reduce the pairing gap.

The results depend on the effective interaction used.

The balance between density and spin fluctuations is crucial.

Abstract

The 1S0 pairing gap associated with the inner crust of a neutron star is calculated, taking into account the coexistence of the nuclear lattice with the sea of free neutrons (finite size effects), as well as medium polarization effects associated with the exchange of density and spin fluctuations. Both effects are found to be important and to lead to an overall quenching of the pairing gap. This result, whose quantitative value is dependent on the effective interaction used to generate the single-particle levels, is a consequence of the balance between the attractive (repulsive) induced interaction arising from the exchange of density (spin) modes, balance which in turn is influenced by the presence of the protons and depends on the single-particle structure of the system.