Electroweak Vacuum Stability and the Higgs Field Relaxation via Gravitational Effects

TL;DR

This paper explores how gravitational effects in the early universe, specifically through a non-minimal coupling to higher-curvature gravity, can influence Higgs field dynamics, potentially stabilizing the electroweak vacuum without new physics beyond the Standard Model.

Contribution

It introduces a two-parameter model with non-minimal Higgs coupling to higher-curvature gravity, predicting enhanced Higgs self-coupling and lifting scalar flat directions via gravitational effects.

Findings

Higgs initially undergoes fast oscillations due to large effective mass.

Weyl field slowly rolls on a plateau-like potential after oscillations.

Higgs self-coupling in the EW vacuum is enhanced compared to SM predictions.

Abstract

The measured values of the Standard Model (SM) parameters favors a shallow metastable electroweak (EW) vacuum surrounded by a deep global AdS or a runaway Minkowski minimum. Furthermore, fine-tuning is the only explanation for the Higgs relaxing in its present local minimum. In this paper, assuming no new physics beyond the SM, we study the universal effect of gravity on the Higgs dynamics in the early universe. A generic two-parameter model is considered in which the Higgs is non-minimally coupled to a higher-curvature theory of gravity. The coupling between the Higgs field and the Weyl field in the Einstein frame has genuine predictions. In a broad region in the parameter space, the effective Higgs mass is large and it initially takes over through fast oscillations. This epoch is followed by the Weyl field slowly rolling a plateau-like potential. This framework generically predicts that the Higgs self-coupling in the EW vacuum is enhanced, compared to the SM predictions, through couplings to the gravity sector. Moreover, when the Higgs is settled in the EW vacuum, all other scalar flat directions would be lifted via gravitational effects mediated by the Weyl field.