Distinguishing Higgs inflation and its variants
  We consider how Higgs Inflation can be observationally distinguished from
variants based on gauge singlet scalar extensions of the Standard Model, in
particular where the inflaton is a non-minimally coupled gauge singlet scalar
(S-inflation). We show that radiative corrections generally cause the spectral
index n to decrease relative to the classical value as the Higgs mass is
increased if the Higgs boson is the inflaton, whereas n increases with
increasing Higgs mass if the inflaton is a gauge singlet scalar. The accuracy
to which n can be calculated in these models depends on how precisely the
reheating temperature can be determined. The number of Einstein frame
e-foldings N is similar in both models, with N = 58-61 for singlet inflation
compared with N = 57-60 for Higgs inflation. This allows the spectral index to
be calculated to an accuracy \Delta n = 0.001. Provided the Higgs mass is above
~ 135 GeV, a combination of a Higgs mass measurement and a precise
determination of n will enable Higgs Inflation and S-inflation to be
distinguished.
