  We compute the fully renormalized one-loop effective action for two
interacting and self-interacting scalar fields in FRW space-time. We then
derive and solve the quantum corrected equations of motion both for fields that
dominate the energy density (such as an inflaton) and fields that do not (such
as a subdominant curvaton). In particular, we introduce quantum corrected
Friedmann equations that determine the evolution of the scale factor. We find
that in general, gravitational corrections are negligible for the field
dynamics. For the curvaton-type fields this leaves only the effect of the
flat-space Coleman-Weinberg-type effective potential, and we find that these
can be significant. For the inflaton case, both the corrections to the
potential and the Friedmann equations can lead to behaviour very different from
the classical evolution. Even to the point that inflation, although present at
tree level, can be absent at one-loop order.
