111 Chapter 4: Fluctuations in Jet Tomography about the validity of their conclusions. One can readily see in Fig. 4.9 that the use of fluctuating path lengths in a realistic and expanding background medium geometry results in a pre- dicted R$_{AA}$ ( p$_{T}$ ) inconsistent with data when the medium density is artificially increased by a factor of 2. Sensitivity to medium density changes is enhanced over pure radiative loss models by the inclusion of elastic energy loss, due to its smaller width for fluctuations relative to radiative Fig. 4.10. We note, however, that models using GLV-type radiative loss or higher-twist loss only are similarly not fragile [356]. More recent work in which jets were propa- Figure 4.9: Model sensitivity to varying dN$_{g}$/dy , which is much greater than observed in [306]. The susceptibility to changes in the fixed α$_{s}$ suggests the need to investigate the theoretical error stemming from the coupling.