Effects of the temperature and magnetic-field dependent coupling on the properties of QCD matter

TL;DR

This paper studies how temperature- and magnetic-field-dependent couplings influence QCD matter properties, revealing significant effects on thermodynamic quantities and the pseudocritical temperature, especially under strong magnetic fields.

Contribution

It introduces an analytical relation between two criteria for the pseudocritical temperature and explores the impact of running couplings on QCD matter in magnetic fields.

Findings

Running coupling drastically changes quark mass and thermodynamic properties.

Discrepancy between criteria for pseudocritical temperature depends on $dG/dT$ behavior.

Strong magnetic fields influence the relation between coupling and phase transition indicators.

Abstract

To reflect the asymptotic freedom in the thermal direction, a temperature-dependent coupling was proposed in the literature. We investigate its effect on QCD matter with and without strong magnetic fields. Compared with the fixed coupling constant, the running coupling leads to a drastic change in the dynamical quark mass, entropy density, sound velocity, and specific heat. The crossover transition of QCD matter at finite temperature is characterized by the pseudocritical temperature $T_\mathrm{pc}$, which is generally determined by the peak of the derivative of the quark condensate with respect to the temperature $d\phi/dT$, or equivalently, by the derivative of the quark dynamical mass $d M/dT$. In a strong magnetic field, the temperature- and magnetic-field-dependent coupling $G(eB,T)$ was recently introduced to account for inverse magnetic catalysis. We propose an analytical relation between the two criteria $d\phi/dT$ and $dM/dT$ and show a discrepancy between them in finding the pseudocritical temperature. The magnitude of the discrepancy depends on the behavior of $dG/dT$.