Scalaron-Higgs inflation

TL;DR

Scalaron-Higgs inflation combines the Standard Model Higgs with quadratic curvature to produce inflationary models that align with Higgs or Starobinsky inflation, and explores implications of small Higgs self-coupling for early universe dynamics.

Contribution

The paper demonstrates that scalaron-Higgs inflation effectively reduces to known models under certain conditions and analyzes new inflationary behaviors with very small Higgs self-coupling.

Findings

Inflationary predictions match Higgs or Starobinsky inflation for fixed Higgs self-coupling.

Small Higgs self-coupling leads to either enhanced tensor-to-scalar ratio or oscillatory power spectrum features.

Conditions under which small self-coupling arises from Standard Model RG flow are identified.

Abstract

In scalaron-Higgs inflation the Standard Model Higgs boson is non-minimally coupled to gravity and the Einstein-Hilbert action is supplemented by the quadratic scalar curvature invariant. For the quartic Higgs self-coupling $\lambda$ fixed at the electroweak scale, we find that the resulting inflationary two-field model effectively reduces to a single field model with the same predictions as in Higgs inflation or Starobinsky inflation, including the limit of a vanishing non-minimal coupling. For the same model, but with the scalar field a priori not identified with the Standard Model Higgs boson, we study the inflationary consequences of an extremely small $\lambda$. Depending on the initial conditions for the inflationary background trajectories, we find that the two-field dynamics either again reduces to an effective single-field model with a larger tensor-to-scalar ratio than predicted in Higgs inflation and Starobinsky inflation, or involves the full two-field dynamics and leads to oscillatory features in the inflationary power spectrum. Finally, we investigate under which conditions the inflationary scenario with extremely small $\lambda$ can be realized dynamically by the Standard Model renormalization group flow and discuss how the scalaron-Higgs model can provide a natural way to stabilize the electroweak vacuum.