The refractive index in the viscous quark-gluon plasma

TL;DR

This paper investigates how shear viscosity affects the refractive index of the viscous quark-gluon plasma, revealing conditions under which negative refraction occurs and how it varies with viscosity.

Contribution

It derives the gluon self-energy in viscous chromohydrodynamics and analyzes the resulting refractive index, highlighting the impact of shear viscosity on negative refraction phenomena.

Findings

Refractive index becomes negative in certain frequency ranges.

Negative refraction range widens with increasing shear viscosity.

The start and end points of negative refraction are linked to electric permittivity and magnetic permeability poles.

Abstract

Under the framework of the viscous chromohydrodynamics, the gluon self-energy is derived for the quark-gluon plasma with shear viscosity. The viscous electric permittivity and magnetic permeability are evaluated from the gluon self-energy, through which the refraction index %in the %viscous quark-gluon plasma is investigated. The numerical analysis indicates that the refractive index becomes negative in some frequency range. The start point for that frequency range is around the electric permittivity pole, and the magnetic permeability pole determines the end point. As the increase of $\eta/s$, the frequency range for the negative refraction becomes wider.