Enlarging the parameter space of standard hybrid inflation

Abstract

We show that the parameter space for F-term inflation which predicts the formation of cosmic strings is larger than previously estimated, firstly, because realistic embeddings in GUT theories alter the standard scenario, making the inflationary potential less steep and, secondly, because the strings which form at the end of inflation are not necessarily topologically stable down to low scales. In shifted and smooth inflation, strings do not form at all. We also discuss D-term inflation; here the possibilities are much more limited for enlarging the parameter space.