Low-energy theorems of QCD and bulk viscosity at finite temperature and baryon density in a magnetic field

TL;DR

This paper derives low-energy theorems and expresses bulk viscosity of QCD matter at finite temperature, baryon density, and magnetic field in terms of thermodynamic quantities, enhancing understanding of nonperturbative QCD effects.

Contribution

It introduces new relations between nonperturbative condensates and thermodynamic pressure, and formulates a bulk viscosity expression under combined finite temperature, density, and magnetic field conditions.

Findings

Derived equations linking condensates to thermodynamic pressure.

Expressed bulk viscosity in terms of thermodynamic quantities.

Analyzed various limiting cases of the QCD matter.

Abstract

The nonperturbative QCD vacuum at finite temperature and a finite baryon density in an external magnetic field is studied. Equations relating nonperturbative condensates to the thermodynamic pressure for $T\neq 0$, $\mu_q \neq 0$ and $H\neq 0$ are obtained, and low-energy theorems are derived. A bulk viscosity $\zeta(T, \mu, H)$ is expressed in terms of basic thermodynamical quantities describing the quark-gluon matter at $T\neq 0$, $\mu_q \neq 0$, and $H\neq 0$. Various limiting cases are also considered.