Early-Time Energy Loss in a Strongly-Coupled SYM Plasma

TL;DR

This paper analytically investigates the early-time energy loss of a quark in a strongly-coupled SYM plasma using AdS/CFT, revealing a different temperature scaling and momentum dependence compared to late-time results.

Contribution

It provides the first analytic description of early-time quark energy loss in a strongly-coupled plasma, highlighting new temperature scaling and momentum-dependent friction effects.

Findings

Energy loss scales as T^4 at early times

Friction coefficient depends on quark momentum

Early energy loss is smaller than late-time loss under RHIC conditions

Abstract

We carry out an analytic study of the early-time motion of a quark in a strongly-coupled maximally-supersymmetric Yang-Mills plasma, using the AdS/CFT correspondence. Our approach extracts the first thermal effects as a small perturbation of the known quark dynamics in vacuum, using a double expansion that is valid for early times and for (moderately) ultrarelativistic quark velocities. The quark is found to lose energy at a rate that differs significantly from the previously derived stationary/late-time result: it scales like T^4 instead of T^2, and is associated with a friction coefficient that is not independent of the quark momentum. Under conditions representative of the quark-gluon plasma as obtained at RHIC, the early energy loss rate is a few times smaller than its late-time counterpart. Our analysis additionally leads to thermally-corrected expressions for the intrinsic energy and momentum of the quark, in which the previously discovered limiting velocity of the quark is found to appear naturally.