Thermomagnetic Properties of QCD

TL;DR

This paper investigates how external magnetic fields affect the thermomagnetic properties of QCD at low energies, revealing that magnetic fields decrease entropy density and induce negative magnetization, with implications for chiral symmetry behavior.

Contribution

It provides two-loop chiral perturbation theory calculations of entropy density and magnetization in QCD under magnetic fields, a novel detailed analysis in this regime.

Findings

Entropy density decreases with increasing magnetic field.

Magnetization remains negative across studied parameters.

Finite-temperature quark condensate enhancement correlates with entropy decrease.

Abstract

We explore the low-energy regime of quantum chromodynamics subjected to an external magnetic field by deriving the two-loop representations for the entropy density and the magnetization within chiral perturbation theory (CHPT). At fixed temperature, the entropy density drops when the magnetic field becomes stronger. The magnetization induced at finite temperature is negative in the entire parameter region accessible by CHPT. We also point out that the enhancement of the finite-temperature part in the quark condensate is correlated with the decrease of the entropy density.