Exploring anisotropic effects in magnetized quark matter

We investigate the thermodynamic properties of cold magnetized quark matter within a nonlocal Nambu–Jona-Lasinio 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 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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>e</a:mi> <a:mi>B</a:mi> </a:math> , signaling the occurrence of inverse magnetic catalysis at finite chemical potential. 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.