Electroweak vacuum stability and the Higgs field relaxation via gravitational effects

The measured values of the standard model parameters favors a shallow metastable electroweak vacuum and a deep global minimum. The Higgs relaxation in its present local minimum can only be explained via a large degree of fine-tuning. In this paper, irrespective of new physics beyond the SM, we study the universal effect of gravity on the Higgs dynamics in the early universe. We consider a two-parameter framework in which the Higgs is non-minimally coupled to a higher-curvature gravity. In the Einstein frame there are genuine couplings between the Higgs field and the Weyl field with interesting predictions. In a broad region in the parameter space and for large field values, the effective Higgs mass is large and thus it initially takes over the dynamics by its coherent oscillations. Finally, the Weyl (inflaton) field with its plateau-like potential dominates and derives cosmic inflation. In this framework, the Higgs self-coupling in the electroweak vacuum is modified by contributions from gravity sector. (paper)