Enlarging the parameter space of standard hybrid inflation

TL;DR

This paper broadens the understanding of parameter space in hybrid inflation models, showing that cosmic string formation is less inevitable and more model-dependent than previously thought, especially in GUT embeddings.

Contribution

It demonstrates that realistic GUT embeddings and alternative inflation models like shifted and smooth inflation significantly expand the viable parameter space for hybrid inflation.

Findings

GUT embeddings make the inflationary potential less steep.

Strings formed at inflation end may not be topologically stable.

Shifted and smooth inflation models do not produce strings.

Abstract

We show that the parameter space for F-term inflation which predict the formation of cosmic strings is larger than previously estimated. Firstly, because realistic embeddings in GUT theories alter the standard scenerio, making the inflationary potential less steep. Secondly, 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 to enlargen paramer space.