Screening length in plasma winds
Elena Caceres, Makoto Natsuume, Takashi Okamura
TL;DR
This work investigates the velocity-dependent screening length $L_s$ of a heavy quark–antiquark pair in strongly coupled plasmas using AdS/CFT, focusing on the ultra-relativistic regime. It develops a general method to extract the scaling exponent $\nu$ governing $L_s$, showing that conformal theories yield $L_s \propto (\text{boosted energy density})^{-1/d}$ while non-conformal backgrounds yield smaller exponents related to the speed of sound. Through explicit analyses of ${\rm SAdS}_{d+1}$, R-charged black holes, Klebanov–Tseytlin, and D$p$-brane geometries, the authors demonstrate that, in conformal cases, the exponent is robustly determined by dimensionality, whereas non-conformal theories exhibit deviations tied to $c_s^2$ via a proposed universal relation. The results imply that, near temperatures relevant to heavy-ion collisions, QCD may be well approximated by conformal scaling since lattice data indicate $c_s^2$ close to $1/3$, while offering a quantitative framework to gauge non-conformal effects and their impact on quarkonium suppression in a flowing plasma.
Abstract
We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.