Unitarizing Higgs Inflation

Understand

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.