2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/154211The goal of these notes is to give a brief explanation of how electric-magnetic duality in four dimensions is related to the existence of an unusual conformal field theory in six dimensions.16 pp; lectures presented at the Conference On Topology, Geometry, and Quantum Field Theory (Oxford University, 2002); minor error corrected in v. 2Representation TheoryMathematical Physicstext