Folded Resonant Non-Gaussianity in General Single Field Inflation
  We compute a novel type of large non-Gaussianity due to small periodic
features in general single field inflationary models. We show that the
non-Bunch-Davies vacuum component generated by features, although has a very
small amplitude, can have significant impact on the non-Gaussianity. Three
mechanisms are turned on simultaneously in such models, namely the resonant
effect, non-Bunch-Davies vacuum and higher derivative kinetic terms, resulting
in a bispectrum with distinctive shapes and running. The size can be equal to
or larger than that previously found in each single mechanism. Our full
results, including the resonant and folded resonant non-Gaussianities, give the
leading order bispectra due to general periodic features in general single
field inflation.
