Higgs xi-inflation for the 125-126 GeV Higgs: a two-loop analysis

TL;DR

This paper re-evaluates Higgs xi-inflation with a 125-126 GeV Higgs, showing that smaller non-minimal coupling xi (~90-400) can still produce viable inflationary models with observable tensor-to-scalar ratios, using two-loop calculations.

Contribution

It demonstrates that lower values of xi are sufficient for Higgs inflation when considering two-loop effects and the specific Higgs mass range, challenging previous assumptions.

Findings

Viable inflation with xi as low as 90-400.

Potential for observable tensor-to-scalar ratio r.

No second minimum in the Higgs potential at these xi values.

Abstract

A non-minimal coupling xi of the Standard Model Higgs field to gravity can give rise to inflation, but large xi is required and thus leads to a violation of perturbative unitarity at Mp/xi, which is well below the inflationary scale Mp/sqrt(xi). We re-examine this claim for a Higgs mass in the range 125-126 GeV for which lambda_eff(mu) runs to very small values near the Planck scale and can significantly reduce the value of xi required for inflation. Using the two-loop renormalization group equations and effective potential for Higgs xi-inflation, we find that familiar inflationary solutions can have a non-minimal coupling as small as xi ~ 400 without the potential developing a second minimum. We also find a new observationally allowed region of Higgs xi-inflation with xi ~ 90 and distinct inflationary predictions, including an observable level of the tensor-to-scalar ratio r.