Exploring Anisotropic Effects in Magnetized Quark Matter

TL;DR

This paper studies how strong magnetic fields affect the thermodynamic properties of quark matter using a nonlocal NJL model, revealing anisotropic pressures, magnetic catalysis, inverse magnetic catalysis, and oscillatory magnetic susceptibility.

Contribution

It provides a detailed analysis of anisotropic effects and magnetic phenomena in magnetized quark matter, including the impact of finite quark masses on phase transitions.

Findings

Magnetic fields induce anisotropic pressures and enhance the speed of sound along the field.

Quark density increases with magnetic field, showing magnetic catalysis.

Inverse magnetic catalysis occurs at finite chemical potential and strong magnetic fields.

Abstract

We investigate the thermodynamic properties of cold magnetized quark matter within a nonlocal Nambu Jona Lasinio (nlNJL) model. Our study addresses the equation of state, anisotropic pressures, quark density, speed of sound, and magnetic susceptibility, with direct comparison to the chiral limit. Strong magnetic fields are found to generate marked anisotropy: the longitudinal pressure and speed of sound are enhanced, approaching the causal bound in the lowest Landau-level (LLL) regime, while the transverse components are systematically reduced. The quark density exhibits magnetic catalysis, increasing with both the chemical potential and the magnetic field strength. At moderate to high fields, the critical chemical potential decreases with increasing $eB$, signaling the occurrence of inverse magnetic catalysis at finite chemical potential ($\mu$IMC). Magnetic susceptibility displays oscillations around zero in low fields, driven by de Haas van Alphen like effects, and settles at positive values for strong fields, consistent with an overall growth of magnetization. Compared with the chiral limit, the inclusion of finite current quark masses does not modify the overall oscillatory behavior, but changes the nature of the Landau level transitions, which become weakly first order instead of second order.