Degeneracy in the spectrum and bispectrum among featured inflaton
  potentials
  We study the degeneracy of the primordial spectrum and bispectrum of the
curvature perturbation in single field inflationary models with a class of
features in the inflaton potential. The feature we consider is a discontinuous
change in the shape of the potential and is controlled by a couple of
parameters that describe the strength of the discontinuity and the change in
the potential shape. This feature produces oscillations of the spectrum and
bispectrum around the comoving scale $k=k_0$ that exits the horizon when the
inflaton passes the discontinuity. We find that the effects on the spectrum and
almost all configurations of the bispectrum including the squeezed limit depend
on a single quantity which is a function of the two parameters defining the
feature. This leads to a degeneracy, i.e. different features of the inflaton
potential can produce the same observational effects. However, we find that the
degeneracy in the bispectrum is removed at the equilateral limit around
$k=k_0$. This can be used to discriminate different models which give the same
spectrum.
