124 Chapter 5: pQCD vs. AdS/CFT problem into a modern string theoretic version of the 1696 Brachistochrone problem and yields a remarkable, simple analytic solution for the string shape and momentum loss per unit time. Exploiting the AdS/CFT correspondence, the drag coefficient for a massive quark moving through a strongly-coupled SYM plasma in the λ = g 2 $_{SY M}$N$_{c}$ ≫ 1, N$_{c}$ ≫ 1, M$_{Q}$ ≫ T ∗ limit is given in [342, 343, 347] as 5.2 AdS/CFT compared to pQCD dp$_{T}$ dt = − µ$_{Q}$p$_{T}$ = − π √ λ ( T $^{∗}$) 2 2 M$_{Q}$ p$_{T}$, (5.1) dp$_{T}$ dt ∼ − T 3 M $_{2}$p$_{T}$ , (5.2) dp$_{T}$ dt ∼ − LT $^{3}$log( p$_{T}$/M ) . (5.3) where T ∗ is the temperature of the SYM plasma as fixed by the Hawking temperature of the dual D3 black brane. This is parametrically quite similar to the Bethe-Heitler limit of incoherent radiative energy loss, in which case differing from Eq. (5.1) only by a factor of T/M , and quite dissimilar to the usual LPM-dominated asymptotic pQCD result, There exists a maximum momentum, or γ$_{c}$ ≈ p crit T /M$_{Q}$ beyond which Eq.