Holographic dual of collimated radiation

TL;DR

This paper introduces a new method using AdS/CFT to estimate radiation from an accelerated quark, explaining the collimated nature of synchrotron radiation via gravitational shock waves, simplifying boundary stress tensor calculations.

Contribution

It presents a heuristic approach linking string backreaction to shock waves, simplifying the computation of radiation patterns in strongly coupled media.

Findings

Backreaction of a relativistic string is modeled by superimposed shock waves.

Boundary stress tensor calculation reduces to geodesic analysis in AdS.

The method explains collimated radiation in strongly coupled systems.

Abstract

We propose a new and simple method of estimating the radiation due to an accelerated quark in a strongly coupled medium, within the framework of the AdS/CFT correspondence. In particular, we offer a heuristic explanation of the collimated nature of synchrotron radiation produced by a circling quark, which was recently studied in Phys.Rev.D81 (2010) 126001. The gravitational dual of such quark is a coiling string in AdS, whose backreaction on the spacetime geometry remains tightly confined, as if 'beamed' towards the boundary. While this appears to contradict conventional expectations from the scale/radius duality, we resolve the issue by observing that the backreaction of a relativistic string is reproduced by a superposition of gravitational shock waves. We further demonstrate that this proposal allows us to reduce the problem of computing the boundary stress tensor to merely calculating geodesics in AdS, as opposed to solving linearized Einstein's equations.