Magnetic Monopoles, Vortices and the Topology of Gauge Fields

Lattice calculations performed in Abelian gauges give strong evidence that confinement is realized as a dual Meissner effect, implying that the Yang-Mills vacuum consists of a condensate of magnetic monopoles. Alternative lattice caluclations performed in the maximum center gauge give strong support that center vortex configurations are the relevant infrared degrees of freedom responsible for confinement and that the magnetic monopoles are mostly sitting on vortices. In this talk I study the continuum Yang-Mills-theory in Abelian and center gauges. In Polyakov gauge the Pontryagin index of the gauge field is expressed by the magnetic monopole charges. The continuum analogues of center vortices and the continuum version of the maximum center gauge are presented. It is shown that the Pon-tryagin index of center vortices is given by their self-intersection number, which vanishes unless magnetic monopole currents are flowing on the vortices.