Thermal photon production in a strongly coupled anisotropic plasma

TL;DR

This paper uses gauge/gravity duality to compute photon production rates in a strongly coupled anisotropic plasma, revealing that anisotropy generally increases photon emission compared to isotropic conditions.

Contribution

It provides the first detailed calculation of photon production and electromagnetic correlators in an anisotropic, strongly coupled plasma using holography.

Findings

Total photon production rate is always higher than isotropic case.

Photon emission depends on direction and polarization, varying relative to anisotropy.

Correlation functions and electric conductivity are affected by anisotropy.

Abstract

Photons produced in heavy ion collisions escape virtually unperturbed from the surrounding medium, thus representing an excellent probe of the conditions at the emission point. Using the gauge/gravity duality, we calculate the rate of photon production in an anisotropic, strongly coupled N=4 plasma with Nf<<Nc quark flavors. We consider arbitrary orientations of the photon momentum with respect to the anisotropic direction, as well as arbitrary values of the anisotropy. We present results for the correlation functions of two electromagnetic currents and for the electric conductivity. These quantities can be larger or smaller than the isotropic ones, depending on the direction of propagation and polarization of the photons. The total production rate is however always larger than the isotropic one, independently of the frequency, direction of propagation, and value of the anisotropy.