Lee-Yang zeros and the chiral phase transition in compact lattice QED

In this paper we present a detailed study of the phase structure in the β-m plane for compact lattice QED. We analyze the scaling properties of the distribution of the partition function zeros in the complex fermion mass plane on $4^4$, $6^4$, $8^4$, and ${10}^4$ lattices. The partition function is numerically evaluated by using two independent methods, based, respectively, on a standard HMC (hybrid Monte Carlo) program and on an alternative approach derived from the MFA (microcanonical fermionic average). The finite size scaling behavior gives strong indications for a first-order phase transition at any value of the fermion mass. The reliability of the result follows from the remarkable agreement between the two independent methods.