Ultraviolet behaviour of Higgs inflation models

We study the ultraviolet behaviour of Higgs inflation models above the apparent unitarity violation scale arising from the large non minimal coupling to gravity, by computing on-shell 4-point scattering amplitudes in the presence of a large inflaton background, away from the electroweak vacuum. We find that all tree-level amplitudes are well behaved at high energies below the inflaton background that can thus take values up to the Planck scale. This result holds in both the metric and Palatini formulation, and is independent of the frame (Jordan or Einstein) as expected. The same result also holds if an R-2 term is added to the action.

Automated summary

In this study, we investigate the ultraviolet behavior of Higgs inflation models above the apparent unitarity violation scale caused by the large non minimal coupling to gravity. By computing on-shell 4-point scattering amplitudes in the presence of a large inflaton background, we find that all tree-level amplitudes behave well at high energies below the inflaton background. This result holds true in both the metric and Palatini formulation, regardless of the frame used (Jordan or Einstein), and remains consistent even when an R-2 term is added to the action.