Flattened Axion Monodromy Beyond Two Derivatives
  We study string inspired two-field models of large-field inflation based on
axion monodromy in the presence of an interacting heavier modulus. This class
of models has enough structure to approximate at least part of the backreaction
effects known in full string theory, such as kinetic mixing with the axion, and
flattening of the scalar potential. Yet, it is simple enough to fully describe
the structure of higher-point curvature perturbation interactions driven by the
adjusting modulus backreaction dynamics. We find that the presence of the heavy
modulus can be described via two equivalent effective field theories, both of
which can incorporate reductions of the speed of sound. Hence, the presence of
heavier moduli in axion monodromy inflation constructions will necessarily
generate some amount of non-Gaussianity accompanied by changes to $n_s$ and $r$
beyond what results from just from the well known adiabatic flattening
backreaction.
