Parity solves the Strong CP problem
Ravi Kuchimanchi · arXiv (Cornell University) · 2025
A recent paper "What can solve the strong CP problem?" goes counter to conventional wisdom by arguing that the universe was in an initial state that combines different eigenstates of $θ$ (of the theta vacuum of QCD), and asserts that for such an initial state, axionless solutions to the Strong CP Problem based on P and CP symmetries will not work. We discuss the nature of the theta vacuum in light of this work, and find that the conventional framing and solutions based on P and CP symmetries are on a firm footing.