Contributor info: Prof. Matthew Reece

Daniel Aloni, Eduardo García-Valdecasas, Matthew Reece, Motoo Suzuki

SciPost Phys. 17, 031 (2024) · published 1 August 2024 | Toggle abstract · pdf

Spontaneous breaking of symmetries leads to universal phenomena. We extend this notion to $(-1)$-form U(1) symmetries. The spontaneous breaking is diagnosed by a dependence of the vacuum energy on a constant background field $\theta$, which can be probed by the topological susceptibility. This leads to a reinterpretation of the Strong CP problem as arising from a spontaneously broken instantonic symmetry in QCD. We discuss how known solutions to the problem are unified in this framework and explore some, so far unsuccessful, attempts to find new solutions.