Vacuum structure of compact lattice QED

We investigate compact lattice QED at finite temperature on a 4-dimensional spacetime lattice with and without dynamical fermions and interpret our results in the dual superconductor picture. In the presence of dynamical fermions the linear plus Coulomb intercharge potential of pure U(1) theory at strong couplings becomes screened due to the breaking of the confinement string. At weak couplings the effect of fermion loops is small. Analyzing the energy density around a charge-anticharge pair we visualize the formation and the breaking of the flux tube and estimate the string thickness in both coupling phases. The fermionic vacuum around static electric charges is investigated by correlating the local chiral condensate and the virtual charge density with Polyakov loops. A static charge polarizes the vacuum like in ordinary QED, attracts virtual anticharges and repulses virtual charges which leads to a net charge excess of opposite sign around static sources. The chiral condensate is suppressed in the vicinity of a static electron. This means that chiral symmetry is partially restored close to external charges. For both observables the effect is more pronounced at strong couplings and increases with decreasing bare fermion mass