A GUIDE TO FLAT DIRECTION ANALYSIS IN ANOMALOUS U(1) MODELS

We suggest a systematic procedure to study D- and F-flat directions in a large class of models with an anomalous U(1). This class of models is characterized by the existence of a vacuum that breaks all Abelian gauge symmetries connecting the observable sector to the hidden sector . We show that, under some conditions, there is no other stable vacuum that breaks these symmetries. As a consequence, the model yields defi nite (order of magnitude) predictions for low-energy mass hierarchies. Then we study generic flat directions and identify the ones that may lead to undesirable vacua. We give necessary conditions for those to b e Lifted, and show that supersymmetry breaking only slightly affects t he conclusions from the flat direction analysis. (C) 1998 Elsevier Sci ence B.V.