Some remarks on theUA(1)problem in gauge theories of the strong interaction

Abstract

Previously proposed solutions to the $U_A\mathrm{}\left(1\right)\mathrm{}$ problem, or ninth axial-vector current problem, are reviewed and a new solution proposed. We point out that in the presence of magnetic gauge charges the anomalous term $F_{\alpha \beta }^a{}_{}{}^{*}{}_{}{}^{}F_{\alpha \beta }^a{}_{}{}^{}$ is not a total divergence. This implies that the $U_A\mathrm{}\left(1\right)\mathrm{}$ symmetry is explicitly broken.