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 τπ on the energy loss. We find that the collisional
energy loss depends appreciably on τπ . In particular, for typical
values of the viscosity-to-entropy ratio, we show that the energy loss obtained
using τπ = 0 can be ∼ 10% larger than the one obtained using
τπ = 0. Moreover, we find that the energy loss obtained using the
kinetic theory expression for τπ is much larger that the one obtained
with the τπ 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.Comment: v2: 5 pages, 4 figures, added references. Accepted for publication in
Phys. Rev.