Ultra Slow-Roll Inflation and the non-Gaussianity Consistency Relation
  Ultra slow-roll inflation has recently been used to challenge the
non-Gaussianity consistency relation. We show that this inflationary scenario
belongs to a one parameter class of models and we study its properties and
observational predictions. We demonstrate that the power spectrum remains
scale-invariant and that the bi-spectrum is of the local type with
fnl=5(3-ns)/4 which, indeed, represents a modification of the consistency
relation. However, we also show that the system is unstable and suffers from
many physical problems among which is the difficulty to correctly WMAP
normalize the model. We conclude that ultra slow-roll inflation remains a very
peculiar case, the physical relevance of which is probably not sufficient to
call into question the validity of the consistency relation.
