A Model Independent Approach to (p)Reheating
  In this note we propose a model independent framework for inflationary
(p)reheating. Our approach is analogous to the Effective Field Theory of
Inflation, however here the inflaton oscillations provide an additional source
of (discrete) symmetry breaking. Using the Goldstone field that non-linearly
realizes time diffeormorphism invariance we construct a model independent
action for both the inflaton and reheating sectors. Utilizing the hierarchy of
scales present during the reheating process we are able to recover known
results in the literature in a simpler fashion, including the presence of
oscillations in the primordial power spectrum. We also construct a class of
models where the shift symmetry of the inflaton is preserved during reheating,
which helps alleviate past criticisms of (p)reheating in models of Natural
Inflation. Extensions of our framework suggest the possibility of analytically
investigating non-linear effects (such as rescattering and back-reaction)
during thermalization without resorting to lattice methods. By construction,
the EFT relates the strength of many of these interactions to other operators
in the theory, including those responsible for the efficiency of (p)reheating.
We conclude with a discussion of the limitations and challenges for our
approach.
