Enhancing the Jet Quenching Parameter from Marginal Deformations

TL;DR

The paper investigates whether marginal deformations of ${\cal N}=4$ SYM, implemented via AdS/CFT, can enhance the jet quenching parameter $\hat{q}$ beyond its known strong-coupling value. It uses a solution-generating approach to construct deformed gravity duals, showing that sigma deformations amplify $\hat{q}$ by a factor $\sqrt{H}$ (with $H\ge 1$) for purely radial strings, while gamma deformations have no effect in this setup. Extending to nonsupersymmetric deformations reveals more endpoint configurations in internal space that can further enhance $\hat{q}$, highlighting the sensitivity of transport coefficients to internal-space structure. The results suggest a route to bring holographic predictions closer to RHIC data and motivate exploration of more realistic backgrounds and transport phenomena, albeit with caveats related to the warp-factor dependence on internal coordinates and potential nonuniversal behavior.

Abstract

A number of recent papers have applied the AdS/CFT correspondence to a strong-coupling calculation of the medium-induced radiative parton energy loss in nucleus-nucleus collisions at RHIC. The predicted value of the "jet quenching parameter" q, however, is rather small compared to the experimental results. For hot N=4 supersymmetric Yang-Mills theory, certain marginal deformations can have the effect of enhancing q. This result is highly sensitive to the location of the fundamental string's endpoints in the internal space.

Figures (3)

• Figure 1: Marginal deformations of conformal field theories can change the properties of the theories at finite temperature. In particular, $\sigma$ deformations can lead to an enhancement of the "jet quenching parameter" $\hat{q}$.
• Figure 2: Generating new solutions via U-dualities.
• Figure 3: The thermal expectation value of a Wilson loop can be calculated on the supergravity side by considering a fundamental string in the background of an AdS black hole. The string endpoints lie on a probe brane at large distance and the string's turning point is on the black hole horizon. However, this picture is slightly misleading because the directions along the probe brane are actually orthogonal to those along the horizon.