Synchrotron radiation in strongly coupled conformal field theories

TL;DR

This paper uses gauge/gravity duality to analyze synchrotron radiation emitted by a quark in strongly coupled ${ m N}=4$ SYM theory, revealing similarities with classical electrodynamics and providing universal results for strongly coupled conformal field theories.

Contribution

It computes the energy density and angular distribution of radiation from a circularly moving quark at strong coupling, showing universal features across conformal theories with gravity duals.

Findings

Angular distribution of radiation matches weak coupling results up to a prefactor

Radiation is emitted in a narrow beam with opening angle ~1/γ

Emitted radiation appears as periodic bursts similar to lighthouse beams

Abstract

Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled ${\cal N}=4$ supersymmetric Yang-Mills (SYM) theory. We compare the strong coupling results to those at weak coupling, and find the same angular distribution of radiated power, up to an overall prefactor. In both regimes, the angular distribution is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle $\alpha \sim 1/\gamma$. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.