Strongly coupled compact lattice QED with staggered fermions

We explore the compact U(1) lattice gauge theory with staggered fermions and gauge field action - Sigma(p)[beta cos(Theta p) + gamma cos(2 Theta p)], both for dynamical fermions and in the quenched approximation. (Theta p denotes the plaquette angle.) In simulations with dynamical fermions at various gamma less than or equal to -0.2 on 6(4) lattices we find the energy gap at the phase transition of a size comparable to the pure gauge theory for gamma less than or equal to 0 on the same lattice, diminishing with decreasing gamma. This suggests a second-order transition in the thermodynamic limit of the theory with fermions for gamma below some finite negative value. Studying the theory on large lattices at gamma = -0.2 in the quenched approximation by means of the equation of state we find non-Gaussian values of the critical exponents associated with the chiral condensate, beta(chi) similar or equal to 0.32 and delta similar or equal to 1.8, and determine the scaling function. Furthermore, we evaluate the meson spectrum and study the PCAC relation. (C) 1998 Elsevier Science B.V.