  The 750 GeV resonance observed by ATLAS and CMS may be explained by a gauge
singlet scalar. This would provide an ideal candidate for a gauge singlet
scalar alternative to Higgs Inflation, S-inflation. Here we discuss the
relevant results of S-inflation in the context of the 750 GeV resonance. In
particular, we show that a singlet scalar, if it is real, has a major advantage
over the Higgs boson with regard to unitarity violation during inflation. This
is because it is possible to restrict the large non-minimal coupling required
for inflation, $\xi \sim 10^5$, to the real singlet scalar, with all other
scalars having $\xi \sim 1$. In this case the scale of unitarity violation
$\Lambda$ is much larger than the inflaton field during inflation. This
protects the inflaton effective potential from modification by the new physics
or strong coupling which is necessary to restore unitarity, which would
otherwise invalidate the perturbative effective potential based on Standard
Model physics. This is in contrast to the case of Higgs Inflation or models
based on complex singlet scalars, where the unitarity violation scale during
inflation is less than or of the order of the inflaton field. Therefore if the
750 GeV resonance is the inflaton, it must be a non-minimally coupled real
singlet scalar.
