129 Chapter 5: pQCD vs. AdS/CFT N$_{f}$ = 3. As emphasized in [152], detailed geometric path length averaging plays a crucial role in allowing consistency between π $^{0}$, η and heavy quark quenching in pQCD. For AdS/CFT drag, Eq. (5.1) gives the average fractional energy loss as ¯ ϵ = 1 − exp( − µ$_{Q}$ℓ ). Energy loss is assumed to start at thermalization, τ$_{0}$ ∼ 0 . 6 − 1 . 0 fm/c, and stops when the confinement temperature, T$_{c}$ ∼ 160 MeV, is reached. The exponentiated T 2 dependence in µ$_{Q}$ leads to a significant sensitivity to the opacity of the medium, as well as to τ$_{0}$ and T$_{c}$ . To understand the generic qualitative features of our numerical results it is instructive to consider the simplest case of a geometric path average over a static, finite, uniform plasma of thickness L ; then where the p$_{T}$ dependence is carried entirely by the spectral index n$_{Q}$ ( p$_{T}$ ). Two implementations of pQCD energy loss are used in this paper. The first is the full WHDG model convolving fluctuating elastic and inelastic loss with fluctuating path geometry [152]. The second restricts WHDG to include only radiative loss in order to facilitate comparison to [270]. Note that when realistic nuclear geometries with Bjorken expansion are used, the “fragility” of R$_{AA}$ for large ˆ q reported in [306] is absent in both implementations of WHDG. R Q $_{AA}$( p$_{T}$ ) = 1 − e n$_{Q}$µ$_{Q}$L n$_{Q}$µ$_{Q}$L ≈ 1 n$_{Q}$µ$_{Q}$L , (5.5) Unlike the AdS/CFT dynamics, pQCD predicts [152, 298, 374] that the average energy loss fraction in a static uniform plasma is approximately ¯ ϵ ≈