Quark magnetar in three-flavor Nambu--Jona-Lasinio model with vector interaction and magnetized gluon potential

TL;DR

This paper explores the effects of vector interactions and magnetized gluons on strange quark matter within the NJL model under strong magnetic fields, aiming to understand quark star properties and stability.

Contribution

It introduces the combined impact of vector-isoscalar interactions and magnetized gluons on the equation of state and sound velocity in magnetized strange quark matter, relevant for quark star modeling.

Findings

Vector-isoscalar interaction stiffens the equation of state.

Magnetized gluons increase the sound velocity, potentially up to 1.

Conditions for forming 2 solar mass quark magnetars are identified.

Abstract

We investigate properties of strange quark matter in the framework of SU(3) Nambu--Jona-Lasinio(NJL) model with vector interaction under strong magnetic fields. The effects of vector-isoscalar and vector-isovector interaction on the equation of state of strange quark matter are investigated, and it is found that the equation of state is not sensitive to the vector-isovector interaction, however, a repulsive interaction in the vector-isoscalar channel gives a stiffer equation of state for cold dense quark matter. In the presence of magnetic field, gluons will be magnetized via quark loops, and the contribution from magnetized gluons to the equation of state is also estimated. The sound velocity square is a quantity to measure the hardness or softness of dense quark matter, and in the NJL model without vector interaction at zero magnetic field the sound velocity square is always less than 1/3. It is found that a repulsive vector-isoscalar interaction and a positive pressure contribution from magnetized gluons can enhance the sound velocity square, which can even reach 1. To construct quark magnetars under strong magnetic fields, we consider anisotropic pressures and use a density-dependent magnetic field profile to mimic the magnetic field distribution in a quark star. We also analyze the parameter region for the magnitude of vector-isoscalar interaction and the contribution from magnetized gluons in order to produce 2 solar mass quark magnetars.