F-term hybrid inflation in effective supergravity theories

We show that a particular class of effective low energy supergravity theories motivated by string theory can provide a promising framework for models of hybrid inflation in which the potential energy which drives inflation originates from the F-term of the effective supergravity theory. Zn the class of models considered the inflaton is protected from receiving mass during inflation by a generalisation of the Heisenberg symmetry present in no-scale supergravity models. The potential during inflation takes the positive definite form V similar to \Fs\(2) + \F-T\(2) - 3, which allows the possibility that V << m(3/2)(2)M(P)(2) through the cancellation of the positive dilaton and moduli contribution against the negative term. We discuss a toy example where this is realised, then describe the application of this result to realistic models focusing on a particular example in which the mu problem and the strong CP problem are addressed. (C) 1999 Elsevier Science B.V. All rights reserved.