INFLATION FROM SUPERSTRINGS

Abstract

We investigate the possibility of obtaining inflationary solutions from a low energy Lagrangian coming from superstrings. In any viable scheme, the dilaton and the moduli fields have to be stabilized and before this happens, no other field may be used as the inflaton. We show that in a class of models where supersymmetry breaking occurs via gaugino condensation, the dilaton and the moduli fields can be stabilised in a way that enables the use of chiral matter fields in order to obtain enough e-folds of inflation. In a superstring model this is not straightforward, because the form of the Kähler potential is restricted and certain relations between the chiral and moduli fields lead in general to a steep potential. We identify a subclass of Kähler potentials and a certain region of the parameter space of the chiral and moduli fields that may lead to enough inflation. The conditions that we have derived for inflation due to chiral fields are generic and apply also in schemes where the dilaton and moduli fields may be frozen in alternative ways. Demanding that the potential terms associated with the chiral fields do not spoil the dilaton and moduli minimization under the specific scheme that we use to freeze the dilaton, leads to severe constraints on the magnitude of the density fluctuations.