# Dynamical Emergence of Scalaron in Higgs Inflation

## TL;DR

This paper demonstrates that a light scalaron naturally appears in Higgs inflation due to non-minimal coupling, transforming it into a two-field model and resolving unitarity concerns by elevating the cutoff scale to the Planck level.

## Contribution

It reveals the dynamical emergence of the scalaron in Higgs inflation, linking renormalization group effects and scattering amplitudes, and clarifies the model's unitarity properties.

## Key findings

- Scalaron emerges dynamically in Higgs inflation.
- Higgs inflation is effectively a two-field model.
- Unitarity issues are alleviated with the scalaron raising the cutoff to the Planck scale.

## Abstract

We point out that a light scalaron dynamically emerges if scalar fields have a sizable non-minimal coupling to the Ricci scalar as in the Higgs inflation model. We support this claim in two ways. One is based on the renormalization group equation; the non-minimal coupling inevitably induces a Ricci scalar quadratic term due to the renormalization group running. The other is based on scattering amplitudes; a scalar four-point amplitude develops a pole after summing over a certain class of diagrams, which we identify as the scalaron. Our result implies that the Higgs inflation is actually a two-field inflationary model. Another implication is that the Higgs inflation does not suffer from the unitarity issue since the scalaron pushes up the cut-off scale to the Planck scale.