Rose N. Lerner, John McDonald
Unitarity-violation presents a challenge for non-minimally coupled models of
inflation based on weak-scale particle physics. We examine the energy scale of
perturbative unitarity-violation in scattering processes in the presence of a
large inflaton background field for generalized Higgs Inflation models based on
multiple scalar fields. We show that the scale of perturbative
unitarity-violation depends on the individual non-minimal couplings of the
non-inflationary fields. In the case of multiple scalar fields with equal
non-minimal couplings, perturbative unitarity is violated at energies close to
the background field during inflation. This case also applies to Higgs
Inflation, in the limit where the Goldstone bosons can be considered physical.
In contrast, if the non-minimal coupling of the inflaton field is sufficiently
larger than that of the other physical scalars, the background-dependent scale
of unitarity-violation can be much larger than the inflaton field and even than
the effective Planck scale, during inflation. This can be realised in models
where the inflaton is a real singlet scalar (`S-inflation'). We then consider
models which may resolve the issue of unitarity-violation. We argue that the
recent model of Giudice and Lee is not a true completion of Higgs Inflation and
conclude that strong coupling is the most promising direction for a consistent
Higgs Inflation model.
View original:
http://arxiv.org/abs/1112.0954
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