PROGRESS IN UNDERSTANDING CONFINEMENT.

, and is, mod-ulo duality transformation, the same as confinement of magnetic charges ina type 2 superconductor. The end points of an Abrikosov flux tube can beviewed as monopoles; their energy is proportional to the length of the fluxtube, implying that an infinite energy is needed to pull apart at infinite dis-tance a monopole antimonopole pair.However, when going more in detail in the definition of monopoles innon abelian gauge theories, one discovers that monopoles are intrinsecallyU(1) configurations, so that a suitable U(1) must be defined to expose them.The procedure is known as “abelian projection”, and associates a conservedmagnetic charge to any operator in the adjoint representation.Dual superconductivitycan be investigatedin connection with anyabelianprojection. The technique used is to detect if there is condensation ofmonopoles in the confined phase, but not in the deconfined one.A disorder parameter has been defined