# Quark spin polarization and spontaneous magnetization in high density quark matter

## TL;DR

This paper investigates the potential for spin polarization and spontaneous magnetization in high-density quark matter using the NJL model, with implications for magnetic fields in compact stars.

## Contribution

It introduces a tensor-type interaction in the NJL model to demonstrate the possibility of spin polarized phases in quark matter at finite temperature and density.

## Key findings

- Spin polarized phase can exist in quark matter.
- Spontaneous magnetization may occur with quark anomalous magnetic moments.
- Implications for magnetic fields in compact stars are discussed.

## Abstract

By using the Nambu-Jona-Lasinio model with a tensor-type four-point interaction between quarks, it is shown that there exists a possibility of a spin polarized phase in quark matter at finite temperature and density. When there exists the spin polarization, the spontaneous magnetization may occur if the effect of the anomalous magnetic moment of quark is taken into account. An implication to the compact star objects with strong magnetic field is discussed when the spin polarization occurs.