P not PQ

TL;DR

This paper evaluates the simplest parity-based solution to the strong CP problem, considering current experimental constraints and highlighting future prospects for detection through colliders, EDMs, and gravitational waves.

Contribution

It provides a comprehensive assessment of parity solutions in light of recent data and explores new experimental avenues for testing parity breaking.

Findings

Parity solutions remain viable under current constraints

Future collider and gravitational wave experiments can test parity breaking

Parity-based solutions offer a testable alternative to Peccei-Quinn symmetry

Abstract

Parity solutions to the strong CP problem are a compelling alternative to approaches based on Peccei-Quinn symmetry, particularly given the expected violation of global symmetries in a theory of quantum gravity. The most natural of these solutions break parity at a low scale, giving rise to a host of experimentally accessible signals. We assess the status of the simplest parity-based solution in light of LHC data and flavor constraints, highlighting the prospects for near-future tests at colliders, tabletop experiments, and gravitational wave observatories. The origin of parity breaking and associated gravitational effects play crucial roles, providing new avenues for discovery through EDMs and gravity waves. These experimental opportunities underline the promise of generalized parity, rather than Peccei-Quinn symmetry, as a robust and testable solution to the strong CP problem.