Dynamical Emergence of Scalaron in Higgs Inflation
  We point out that a light scalaron dynamically emerges if scalar fields have
a sizable non-minimal coupling to the Ricci scalar as in the Higgs inflation
model. We support this claim in two ways. One is based on the renormalization
group equation; the non-minimal coupling inevitably induces a Ricci scalar
quadratic term due to the renormalization group running. The other is based on
scattering amplitudes; a scalar four-point amplitude develops a pole after
summing over a certain class of diagrams, which we identify as the scalaron.
Our result implies that the Higgs inflation is actually a two-field
inflationary model. Another implication is that the Higgs inflation does not
suffer from the unitarity issue since the scalaron pushes up the cut-off scale
to the Planck scale.
