Acceleration, Energy Loss and Screening in Strongly-Coupled Gauge Theories

TL;DR

This paper investigates the dynamics of heavy quarks in strongly-coupled gauge theories using AdS/CFT, revealing how energy loss, screening, and dispersion relations are affected by external forces and plasma conditions.

Contribution

It provides new insights into quark energy loss, screening lengths, and the effects of external forces in strongly-coupled gauge theories via holographic methods.

Findings

Energy loss rate initially insensitive to plasma conditions

Velocity-dependent screening length is drastically modified at ultra-relativistic speeds

Distinction between singlet and adjoint quark-antiquark configurations in plasma

Abstract

We explore various aspects of the motion of heavy quarks in strongly-coupled gauge theories, employing the AdS/CFT correspondence. Building on earlier work by Mikhailov, we study the dispersion relation and energy loss of an accelerating finite-mass quark in N=4 super-Yang-Mills, both in vacuum and in the presence of a thermal plasma. In the former case, we notice that the application of an external force modifies the dispersion relation. In the latter case, we find in particular that when a static heavy quark is accelerated by an external force, its rate of energy loss is initially insensitive to the plasma, and there is a delay before this rate approaches the value derived previously from the analysis of stationary or late-time configurations. Following up on work by Herzog et al., we also consider the evolution of a quark and antiquark as they separate from one another after formation, learning how the AdS/CFT setup distinguishes between the singlet and adjoint configurations, and locating the transition to the stage where the deceleration of each particle is properly accounted for by a constant friction coefficient. Additionally, we examine the way in which the energy of a quark-antiquark pair moving jointly through the plasma scales with the quark mass. We find that the velocity-dependence of the screening length is drastically modified in the ultra-relativistic region, and is comparable with that of the transition distance mentioned above.