Nature of the phase transition in compact QED

Abstract

The four-dimensional O(2) gauge theory is studied by computer simulations and its phase structure is investigated by three methods: (i) by accurately measuring the action per plaquette on a ${12}^{4}$ lattice, (ii) through a scaling analysis of a certain function of Wilson loops, and (iii) via its string tension. All these methods consistently indicate that the theory has a line of fixed points. The end point of this line exhibits a power-law divergence of the correlation length with index $\ensuremath{\nu}=0.35\ifmmode\pm\else\textpm\fi{}0.05$.