LOCAL BRST COHOMOLOGY OF THE GAUGED PRINCIPAL NONLINEAR SIGMA-MODEL -ART. NO. 025017

The local BRST cohomology of the gauged nonlinear sigma model on a gro up manifold is worked out for any Lie group G. We consider both the ca se where the gauge field is dynamical and the case where it has no kin etic term (G/G topological theory). Our results shed novel light on th e problem of gauging the WZW term as well as on the nature of the topo logical terms introduced a few years ago by DeWit, Hull, and Rocek. We also consider the BRST cohomology of the rigid symmetries of the unga uged model and recover the results of D'Hoker and Weinberg on the most general effective actions compatible with the symmetries. [S0556-2821 (98)06014-7].