Finite size scaling analysis of compact QED

We describe results of a high-statistics finite size scaling analysis of 4d compact U(1) lattice gauge theory with Wilson action at the phase transiti on point. Using a multicanonical hybrid Monte Carlo algorithm we generate d ata samples with more than 150 tunneling events between the metastable stat es of the system, on lattice sizes up to 18(4). We performed a first analys is within the Borgs-Kotecky finite size scaling scheme. As a result, we rep ort evidence for a first-order phase transition with a plaquette energy gap , G = 0.02667(20), at a transition coupling, beta (T) = 1.011128(11).