Double D-term inflation

Comparisons of cosmological models to current data show that the presence o f a non-trivial feature in the primordial power spectrum of fluctuations, a round the scale k similar to 0.05h Mpc(-1), is an open and exciting possibi lity, testable in a near future. This could set new constraints on inflatio nary models. In particular, current data favour a Lambda CDM model with a s teplike spectrum, and more power on small scales. So far, this possibility has been implemented only in toy models of inflation. In this work, we prop ose a supersymmetric model with two U(1) gauge symmetries, associated with two Fayet-Iliopoulos terms. Partial cancellation of the Fayet-Iliopoulos by one of the charged fields generates a step in the primordial power spectru m of adiabatic perturbations. We show that when this field if charged under both symmetries, the spectrum may have more power on small scales. (C) 199 9 Published by Elsevier Science B.V. All rights reserved.