Consistency relations for sharp features in the primordial spectra
  We study the generation of sharp features in the primordial spectra within
the framework of effective field theory of inflation, wherein curvature
perturbations are the consequence of the dynamics of a single scalar degree of
freedom. We identify two sources in the generation of features: rapid
variations of the sound speed c_s (at which curvature fluctuations propagate)
and rapid variations of the expansion rate H during inflation. With this in
mind, we propose a non-trivial relation linking these two quantities that
allows us to study the generation of sharp features in realistic scenarios
where features are the result of the simultaneous occurrence of these two
sources. This relation depends on a single parameter with a value determined by
the particular model (and its numerical input) responsible for the rapidly
varying background. As a consequence, we find a one-parameter consistency
relation between the shape and size of features in the bispectrum and features
in the power spectrum. To substantiate this result, we discuss several examples
of models for which this one-parameter relation (between c_s and H) holds,
including models in which features in the spectra are both sudden and resonant.
