Energy loss of gluons, baryons andk-quarks in an Script N = 4 SYM plasma

We consider different types of external color sources that move through astrongly-coupled thermal N=4 super-Yang-Mills plasma, and calculate, via theAdS/CFT correspondence, the dissipative force (or equivalently, the rate ofenergy loss) they experience. A bound state of k quarks in the totallyantisymmetric representation is found to feel a force with a nontrivialk-dependence. Our result for k=1 (or k=N-1) agrees at large N with the oneobtained recently by Herzog et al. and Gubser, but contains in addition aninfinite series of 1/N corrections. The baryon (k=N) is seen to experience nodrag. Finally, a heavy gluon is found to be subject to a force which at large Nis twice as large as the one experienced by a heavy quark, in accordance withgauge theory expectations.Comment: Latex 2e, 24 pages, 1 eps figure; v2: slightly amplified discussion on the relation between the drag force and the tension of a spatial Wilson loop; v3: minor changes, version to appear in JHE