  Compact U(1) lattice gauge theory in four dimensions is studied by means of
an efficient algorithm which exploits the duality transformation properties of
the model. We focus our attention onto the confining regime, considering the
interquark potential and force, and the electric field induced by two
infinitely heavy sources. We consider both the zero and finite temperature
setting, and compare the theoretical predictions derived from the effective
string model and the dual superconductor scenario to the numerical results.
