# Dynamical Axions and Gravitational Waves

## TL;DR

This paper investigates how dynamical QCD axion models could produce observable gravitational waves during phase transitions, linking axion physics, gravitational wave detection, and collider searches.

## Contribution

It introduces a model connecting dynamical axion-induced phase transitions to gravitational wave signals and collider phenomenology.

## Key findings

- Gravitational wave spectra depend on the axion mass ratio m_{η'}/m_φ.
- Predicted signals are detectable by future gravitational wave experiments.
- TeV-scale states offer collider signatures linked to axion dynamics.

## Abstract

In this paper we explore the possibility of observable gravitational waves as a manifestation of the QCD axion dynamics. In particular, we focus on dynamical axion models which solve the strong CP problem, and include the confinement of a QCD-like gauge group at the TeV scale. We study the resulting chiral symmetry breaking phase transition for models with $N_F=3$ and $N_F=4$ light flavors using the linear sigma model. This model describes the scalar meson spectrum and its interactions, with the diagonal field $\varphi$ as the order parameter. We find that the amplitude of the gravitational wave spectrum depends on the mass of the dynamical axion $\eta'$ via the ratio $m_{\eta'}/m_\varphi$. The resulting spectra may be observed at future mid-range gravitational wave experiments such as AION/MAGIS, DECIGO, and BBO. Moreover, the TeV states can be searched for at colliders and their quantum numbers characterized, providing a unique connection between axion physics, gravitational waves and collider searches.