Confinement and monopoles in lattice QCD

We investigate monopoles defined by different abelian projections, in SU(2) lattice gauge theory. We point out that the usual definition of the monopole density is plagued by lattice artifacts, and that the density is not related to confinement. A modification of the monopole density with respect to the vacuum does exist inside the chromoelectric flux tubes connecting heavy qanti q pairs. However this modification depends on the specific abelian projection used to define monopoles. We argue that the monopole density is not an order parameter for confinement. (orig.)