NJL model of homogeneous neutral quark matter: Pseudoscalar diquark condensates revisited

TL;DR

This paper investigates the phase diagram of dense quark matter under neutron star conditions using a NJL model, focusing on pseudoscalar diquark condensates and their effects on phases like CFLK^0.

Contribution

It revisits the NJL model to include pseudoscalar diquark condensates, revealing new gapless regions and discussing their physical implications in quark matter phases.

Findings

CFLK^0 phase covers large phase diagram regions and is mostly gapped.

A low-temperature gapless CFLK^0 region suggests possible instabilities.

Pseudoscalar condensates influence the 2SC phase properties.

Abstract

We use a Nambu-Jona Lasinio type model to investigate the phase diagram of dense quark matter under neutron star conditions in mean field approximation. The model contains selfconsistently determined quark masses and allows for diquark condensation in the scalar as well as in the pseudoscalar channel. The latter gives rise to the possibility of K^0 condensation in the CFL phase. In agreement with earlier studies we find that this CFLK^0 phase covers large regions of the phase diagram and that the predominant part of this phase is fully gapped. We show, however, that there exists a region at very low temperatures where the CFLK^0 solutions become gapless, possibly indicating an instability towards anisotropic or inhomogeneous phases. The physical significance of solutions with pseudoscalar diquark condensates in the 2SC phase is discussed as well.