F-term Hybrid Inflation in Effective Supergravity Theories

Abstract

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. In 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 $V\sim |F_S|^2 + |F_T|^2 -3$, which allows the possibility that $V\ll m_{3/2}^2 M_P^2$ 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 $μ$ problem and the strong CP-problem are addressed.

23 pages, Latex, 4 eps new figures included; an improved no-scale SUGRA model is presented; section 3 and 5 are new; accepted for publication in Nucl. Phys. B