Monopole currents in U(1) lattice gauge theory: a comparison to an effective model based on dual superconductivity

We compare U(1) lattice gauge theory to an effective model of Maxwell and London equations. In the effective model there is only one free parameter, the London penetration depth λ. It turns out that one can get good agreement between both models if one modifies the usual definition of magnetic monopole currents in U(1) lattice gauge theory. This comparison also shows that already at small distances fluctuations of the occurring string are important. Further, we investigate the β-dependence of the penetration depth and determine the suppression of the monopole condensate in flux tubes.