BTZ Trailing Strings

TL;DR

This paper calculates the energy loss of a moving quark in the D1-D5 CFT using holography, revealing how microstate geometries mimic black-hole physics and identifying special velocities with no drag force.

Contribution

It introduces a holographic method to analyze quark energy loss in microstate geometries, connecting microstate structure to black-hole-like drag forces.

Findings

No drag force when the CFT state has no momentum.

Drag force approaches thermal BTZ behavior as microstate throat length increases.

Existence of a special velocity with no force in non-extremal black holes.

Abstract

We compute holographically the energy loss of a moving quark in various states of the D1-D5 CFT. In the dual bulk geometries, the quark is the end of a trailing string, and the profile of this string determines the drag force exerted by the medium on the quark. We find no drag force when the CFT state has no momentum, and a nontrivial force for any value of the velocity (even at rest) when the string extends in the supersymmetric D1-D5-P black-hole geometry, or a horizonless microstate geometry thereof. As the length of the throat of the microstate geometry increases, the drag force approaches the thermal BTZ expression, confirming the ability of these microstate geometries to capture typical black-hole physics. We also find that when the D1-D5-P black hole is non-extremal, there is a special value of the velocity at which a moving quark feels no force. We compute this velocity holographically and we compare it to the velocity computed in the CFT.