Robustness of Sound Speed and Jet Quenching for Gauge/Gravity Models of Hot QCD

TL;DR

This paper investigates the robustness of a gauge/gravity dual model of hot QCD by analyzing how the speed of sound and jet-quenching parameter vary across different geometries that break conformal symmetry.

Contribution

It constructs a family of geometries solving scalar/gravity equations to test the stability of key QCD observables within the model.

Findings

Speed of sound is universal and robust across geometries.

Jet-quenching parameter varies significantly away from conformal limit.

Dependence of jet-quenching on whether the scalar is dilaton or not.

Abstract

We probe the effectiveness and robustness of a simple gauge/gravity dual model of the QCD fireball that breaks conformal symmetry by constructing a family of similar geometries that solve the scalar/gravity equations of motion. This family has two parameters, one of which is associated to the temperature. We calculate two quantities, the speed of sound and the jet-quenching parameter. We find the speed of sound to be universal and robust over all the geometries when appropriate units are used, while the jet-quenching parameter varies significantly away from the conformal limit. We note that the overall structure of the jet-quenching depends strongly on whether the running scalar is the dilaton or not. We also discuss the variation of the scalar potential over our family of solutions, and truncate our results to where the associated error is small.