69 Chapter 2: Motivation on the r < ∞ boundary of one of these D 7 branes corresponds to a heavy fundamental quark. At zero temperature the geometry supports mesons, with an open string having both its endpoints on D 7 branes. At finite tempera- ture T a string may hang from the D 7 brane and terminate on one of the nonextremal D 3 branes. This is identified with an open heavy quark in a deconfined SYM plasma held at T . One may calculate the Debye screening length for this process, see Fig. 2.14 (a), [337] (and references therein) and also find a small enhancement to q ¯ q dissociation for moving heavy mesons such as J/ Ψ [338, 339]. Given some initial velocity a hanging string will both perturb the Minkowski boundary metric, leaving a wake behind its path in the SYM plasma complete with Mach cones [340, 341] (see Fig. 2.14 (b)), and also lose momentum from its D 7 open heavy flavor endpoint into the D 3 brane horizon [342–344]; see Fig. 2.15. The big payoff from introducing this new complexity is analytic formulae for these intuitively familiar effects. Other applications of the conjecture include calculating the light-like Wil- son loop [338, 345] conjectured to be connected with the jet quenching pa- rameter ˆ q [265] via AdS/CFT, although there is controversy over its ultimate magnitude [346–350]. Also the conjecture was used to investigate the diffusion coefficient in a Langevin formalism [351, 352]; this is only valid in the v → 0 limit [347], and it is not clear what the corrections for nonzero velocity are.