ELECTRIC-MAGNETIC DUALITY, MONOPOLE CONDENSATION, AND CONFINEMENT IN N=2 SUPERSYMMETRIC YANG-MILLS THEORY

We study the vacuum structure and dyon spectrum of N = 2 supersymmetri c gauge theory in four dimensions, with gauge group SU(2). The theory turns out to have remarkably rich and physical properties which can no netheless be described precisely; exact formulas can be obtained, for instance, for electron and dyon masses and the metric on the moduli sp ace of vacua. The description involves a version of Olive-Montonen ele ctric-magnetic duality. The ''strongly coupled'' vacuum turns out to b e a weakly coupled theory of monopoles, and with a suitable perturbati on confinement is described by monopole condensation.