Heavy quark collisional energy loss in the quark-gluon plasma including   finite relaxation time
  In this paper, we calculate the soft-collisional energy loss of heavy quarks traversing the viscous quark-gluon plasma including the effects of a finite relaxation time $\tau_\pi$ on the energy loss. We find that the collisional energy loss depends appreciably on $\tau_\pi$ . In particular, for typical values of the viscosity-to-entropy ratio, we show that the energy loss obtained using $\tau_\pi$ = 0 can be $\sim$ 10$\%$ larger than the one obtained using $\tau_\pi$ = 0. Moreover, we find that the energy loss obtained using the kinetic theory expression for $\tau_\pi$ is much larger that the one obtained with the $\tau_\pi$ derived from the Anti de Sitter/Conformal Field Theory correspondence. Our results may be relevant in the modeling of heavy quark evolution through the quark-gluon plasma. 
Mauro Elias, J. Peralta-Ramos, E. Calzetta
hep-ph nucl-th