Energy Loss of Gluons, Baryons and k-Quarks in an N=4 SYM Plasma
Mariano Chernicoff, Alberto Guijosa
TL;DR
The paper addresses how external color sources dissipate energy while moving in a strongly coupled thermal $N=4$ SYM plasma. It uses the AdS/CFT correspondence to model these sources as D5-branes with electric flux (k-quarks in the antisymmetric representation) and as a pair of D5-branes for a heavy gluon, deriving the drag forces and their dependence on representation and charge, with key formulas revealing a k-dependent factor $ ext{sin}^3 ext{Θ}_k$ and the relation $ rac{ ext{π} k}{N} = ext{Θ}_k - ext{sin} ext{Θ}_k ext{cos} ext{Θ}_k$; the baryon ($k=N$) experiences no drag and the gluon drag is, at large $N$, twice the quark drag. A central technical advance is the inclusion of an end-cap in the D5-brane embedding, which fixes energy and $SU(4)$ charges and resolves energy-charge puzzles. The work connects to $k$-string tensions and spatial Wilson loops, discusses finite-$N$ corrections, and provides holographic predictions for energy loss of multi-quark and adjoint probes relevant to sQGP phenomenology. These results deepen the holographic understanding of parton energy loss and suggest further lattice and theoretical explorations of related Wilson-loop quantities.
Abstract
We consider different types of external color sources that move through a strongly-coupled thermal N=4 super-Yang-Mills plasma, and calculate, via the AdS/CFT correspondence, the dissipative force (or equivalently, the rate of energy loss) they experience. A bound state of k quarks in the totally antisymmetric representation is found to feel a force with a nontrivial k-dependence. Our result for k=1 (or k=N-1) agrees at large N with the one obtained recently by Herzog et al. and Gubser, but contains in addition an infinite series of 1/N corrections. The baryon (k=N) is seen to experience no drag. Finally, a heavy gluon is found to be subject to a force which at large N is twice as large as the one experienced by a heavy quark, in accordance with gauge theory expectations.