Solving the strong CP problem

TL;DR

This paper reviews various solutions to the strong CP problem, including axions, parity, and CP-invariance, and introduces a novel approach involving CP as part of a spontaneously broken flavour symmetry.

Contribution

It presents a new idea that incorporates CP within a spontaneously broken flavour symmetry like U(1) or modular invariance.

Findings

Review of axion, parity, and CP-invariance solutions

Introduction of a novel CP-based approach within flavour symmetry

Proposes a new theoretical framework for the strong CP problem

Abstract

I briefly review solutions to the strong CP problem based on axions, parity invariance, CP-invariance, and present a new idea based on CP as part of a spontaneously broken flavour symmetry such as a U(1) or modular invariance.