Dynamical Wilson fermions and the problem of the chiral limit in compact lattice QED

We compare the approach to the chiral transition line ${\kappa }_c(\text{bt})$ in quenched and full compact lattice QED with Wilson fermions within the confinement phase, especially in the pseudoscalar sector of the theory. We show that in the strong coupling limit ($\beta =0$) the quenched theory is a good approximation to the full one, in contrast to the case of $\beta =0.8$. At the larger $\beta$-value the transition in the full theory is inconsistent with the zero–mass limit of the pseudoscalar particle, thus prohibiting the definition of a chiral limit.