Unitarizing Higgs Inflation
  We consider a simple extension of the Standard Model Higgs inflation with one
new real scalar field which preserves unitarity up to the Planck scale. The new
scalar field (called sigma) completes in the ultraviolet the theory of Higgs
inflation by linearizing the Higgs kinetic term in the Einstein frame, just as
the non-linear sigma model is unitarized into its linear version. The unitarity
cutoff of the effective theory, obtained by integrating out the sigma field,
varies with the background value of the Higgs field. In our setup, both the
Higgs field and the sigma field participate in the inflationary dynamics,
following the flat direction of the potential. We obtain the same slow-roll
parameters and spectral index as in the original Higgs inflation but we find
that the Hubble rate during inflation depends not only on the Higgs
self-coupling, but also on the unknown couplings of the sigma field.
