Inflationary perturbation spectrum in extended effective field theory of
  inflation
  The effective field theory (EFT) of inflation provides a natural framework to
study the new physical effects on primordial perturbations. Recently a healthy
extension of the EFT of inflation with high-order operators has been proposed,
which avoids ghosts and meanwhile leads to a nonlinear dispersion relation of
the scalar perturbations. This paper is devoted to studying the effects of
these high-order operators by using the uniform asymptotic approximation
method. In particular, we first construct the approximate analytical solution
to the mode function of the scalar perturbations. Because of the presence of
the high-order operators, the perturbation modes usually experience a period of
non-adiabatic evolution before they cross the Hubble radius, which could lead
to the production of excited states and modifications of the primordial
perturbation spectrum. However, we show that the modified power spectrum is
still nearly scale-invariant and the presence of the high-order operators can
only affect the overall amplitude of the spectrum. In particular, after showing
explicitly the impact of these new effects on particle production rate and
perturbation spectrum, we explore their origin in detail.
