Nonlinear realizations of compact and noncompact gauge groups

We emphasize the applicability of nonlinear realizations to internal noncompact global invariance groups without apparition of ghosts. The main result is the extension to local invariances. Positive hamiltonians are presented, that generalize the Yang-Mills one for any semi-simple Lie group G. As usual with nonlinear realizations, the (grand unification) G invariance is spontaneously broken down to the linearly realized (compact) subgroup H. (orig.)