# A minimal scale invariant axion solution to the strong CP-problem

## TL;DR

This paper proposes a minimal, scale-invariant extension of the Standard Model that incorporates the KSVZ axion to solve the strong CP problem, linking it with inflation and electroweak physics while avoiding dark matter constraints.

## Contribution

It introduces a novel scale-invariant model where the Peccei-Quinn scalar is identified with the complex dilaton, unifying axion physics with inflation and low-energy phenomena.

## Key findings

- Predicts the existence of TeV-scale coloured fermions.
- Shows the axion has properties similar to KSVZ but does not contribute to dark matter.
- Demonstrates the model's viability for inflation and electroweak physics.

## Abstract

We present a scale invariant extension of the Standard model allowing for the Kim-Shifman-Vainstein-Zakharov (KSVZ) axion solution of the strong CP problem in QCD. We add the minimal number of new particles and show that the Peccei-Quinn scalar might be identified with the complex dilaton field. Scale invariance, together with the Peccei-Quinn symmetry, is broken spontaneously near the Planck scale before inflation, which is driven by the Standard Model Higgs field. We present a set of general conditions which makes this scenario viable and an explicit example of an effective theory possessing spontaneous breaking of scale invariance. We show that this description works both for inflation and low-energy physics in the electroweak vacuum. This scenario can provide a self-consistent inflationary stage and, at the same time, successfully avoid the cosmological bounds on the axion. Our general predictions are the existence of coloured TeV mass fermion and the QCD axion. The latter has all the properties of the KSVZ axion but does not contribute to dark matter. This axion can be searched via it's mixing to a photon in an external magnetic field.