# Fast-Rolling Relaxion

## TL;DR

This paper introduces new mechanisms for stopping a fast-rolling relaxion during inflation, avoiding super-Planckian excursions, and enhancing testability through Higgs mixing, applicable in a broad parameter space.

## Contribution

It proposes novel stopping mechanisms for the relaxion that do not require super-Planckian fields or excessive inflation, expanding the model's viability.

## Key findings

- Mechanisms avoid super-Planckian field excursions.
- Stop relaxion via parametric resonance of the Higgs.
- Relaxion has weak-scale mass and mixes with the Higgs.

## Abstract

We discuss new mechanisms to stop the relaxion field during inflation. They can be realized in a generic model, including the original model but in a quite different parameter region. We consider a fast-rolling relaxion field, which can go over the bumps created by QCD-like dynamics. Then, in one of the mechanisms, we stop it with a parametric resonance of the Higgs field. The mechanisms are free from a super-Planckian field excursion or a gigantic number of e-folds of inflation. The relaxion has a mass around the weak scale and mixes with the Higgs boson, which enhances the testability of our mechanisms.