Gradient Correction to Photon Emission Rate at Strong Coupling

TL;DR

This paper calculates the first-order correction to photon emission rates in a strongly coupled hydrodynamic plasma due to shear velocity gradients, using AdS/CFT correspondence, revealing a significant gradient effect.

Contribution

It introduces a novel calculation of gradient corrections to photon emission rates at strong coupling using real-time holography, providing analytic integral expressions.

Findings

Gradient correction is about 0.3-0.4 times the equilibrium rate.

The correction depends linearly on shear components and temperature.

The method applies real-time holography in AdS/CFT to near-equilibrium plasma.

Abstract

We compute the correction to the photon emission rate in first order of shear components of fluid velocity gradients, $\sigma_{ij}$, in near-equilibrium hydrodynamic plasma at strong coupling regime, using the real-time Schwinger-Keldysh formalism in AdS/CFT correspondence. Our result is an integral of an analytic expression. We observe that the gradient correction to the photon emission rate at strong coupling is about 0.3 - 0.4 times of the equilibrium rate in units of $\sigma_{ij}/T$.