Radiation by a heavy quark in N=4 SYM at strong coupling

TL;DR

This paper calculates the energy radiated by a heavy quark in strongly coupled N=4 SYM using AdS/CFT, revealing classical-like radiation features and discussing artifacts of the supergravity approximation.

Contribution

It provides a novel computation of radiation from a heavy quark at strong coupling via AdS/CFT, highlighting the classical radiation pattern and potential artifacts.

Findings

Energy distribution mimics classical radiation at weak coupling.

Energy density shows anisotropy and negative regions, likely artifacts.

Agreement with previous weak-coupling results for large times.

Abstract

Using the AdS/CFT correspondence in the supergravity approximation, we compute the energy density radiated by a heavy quark undergoing some arbitrary motion in the vacuum of the strongly coupled N=4 supersymmetric Yang-Mills theory. We find that this energy is fully generated via backreaction from the near-boundary endpoint of the dual string attached to the heavy quark. Because of that, the energy distribution shows the same space-time localization as the classical radiation that would be produced by the heavy quark at weak coupling. We believe that this and some other unnatural features of our result (like its anisotropy and the presence of regions with negative energy density) are artifacts of the supergravity approximation, which will be corrected after including string fluctuations. For the case where the quark trajectory is bounded, we also compute the radiated power, by integrating the energy density over the surface of a sphere at infinity. For sufficiently large times, we find agreement with a previous calculation by Mikhailov [hep-th/0305196].