QED on a circle

Abstract

QED with massless fermions on a circle (0\ensuremath{\le}x<L) is exactly solved. The nonintegrable phase exp[ie ${\mathcal{F}}_{0}^{\mathit{L}}$dx ${\mathit{A}}_{1}$(t,x)], which is a dynamical degree of freedom on a circle, couples through the anomaly to the zero mode of the fermion-antifermion bound states, leading to the \ensuremath{\theta} vacuum.