On the Naturalness of Higgs Inflation

TL;DR

This paper critically analyzes the claim that the Standard Model Higgs boson can drive inflation with a strong coupling, arguing that the effective theory breaks down at relevant scales and that the scenario requires unknown ultraviolet physics, undermining its naturalness.

Contribution

The paper demonstrates the limitations of the effective theory approach for Higgs inflation and emphasizes the need for ultraviolet completion to validate the scenario.

Findings

Effective theory breaks down beyond cutoff scale rac{m_p}{\xi}

Extrapolation of Higgs potential beyond cutoff is unwarranted without UV completion

Higgs inflation scenario faces fine-tuning and naturalness issues

Abstract

We critically examine the recent claim that the Standard Model Higgs boson ${\cal H}$ could drive inflation in agreement with observations if $|{\cal H}|^2$ has a strong coupling $\xi\sim 10^4$ to the Ricci curvature scalar. We first show that the effective theory approach upon which that claim is based ceases to be valid beyond a cutoff scale $\Lambda=m_p/\xi$, where $m_p$ is the reduced Planck mass. We then argue that knowing the Higgs potential profile for the field values relevant for inflation ($|{\cal H}|>m_p/\sqrt{\xi}\gg \Lambda$) requires knowledge of the ultraviolet completion of the SM beyond $\Lambda$. In absence of such microscopic theory, the extrapolation of the pure SM potential beyond $\Lambda$ is unwarranted and the scenario is akin to other ad-hoc inflaton potentials afflicted with significant fine-tuning. The appealing naturalness of this minimal proposal is therefore lost.