Generalized gauge theories and the constituents of massless particles

The gauge concept appears in differential geometry; it also appears in particle physics, but with a very different emphasis. In particle physics, especially in quantum field theory, the essential aspect is the appearance of nondecomposable representations of a Lie group. This viewpoint leads to a definition of gauge theories that is wider than that considered in differential geometry (up to now). We study gauge theories in de Sitter space, including gauge theories of scalar and spinor fields. This latter may be associated with a new type of elementary particles with very interesting and unusual properties. Single particle states are unobservable (kinematical confinement) and two-particle states are massless. Dynamical properties will also be mentioned. (orig.)