Absence of CP Violation in the Strong Interaction: Vacuum thwarts Axion

Abstract

QCD admits a contribution to the action, the $\theta$ term, which potentially gives rise to nontrivial phases and violates CP. This is essentially a question of how the vacuum reacts to the $\theta$ term. In this talk I will address the problem using new developments on the lattice. The overall solution is contrasted with the axion `solution'.

Comments: 11 pages, 4 figures; contribution to the 41st International Symposium on Lattice Field Theory (LATTICE2024), 28 July - 3 August 2024, Liverpool, UK