  We investigate the effects of large inhomogeneities in both the inflaton
field and its momentum. We find that in general, large kinetic perturbations
reduce the number of e-folds of inflation. In particular, we observe that
inflationary models with sub-Planckian characteristic scales are not robust
even to kinetic energy densities that are sub-dominant to the potential energy
density. This strengthens the results of our previous work. In inflationary
models with super-Planckian characteristic scales, despite a reduction in the
number of e-folds, inflation is robust even when the potential energy density
is initially sub-dominant. For the cases we study, the robustness of inflation
strongly depends on whether the inflaton field is driven into the reheating
phase by the inhomogeneous scalar dynamics.
