The Standard-smooth Variant of Hybrid Inflation

TL;DR

This paper proposes a two-stage hybrid inflation model within a supersymmetric Pati-Salam framework that resolves the spectral index issue and monopole problem, using only renormalizable interactions.

Contribution

It introduces a novel two-stage inflation scenario combining standard and smooth hybrid inflation within a supersymmetric model, addressing spectral index and monopole issues.

Findings

Achieves acceptable spectral index values by restricting e-foldings during the first inflation stage.

Dilutes monopoles effectively through the second inflation stage.

Provides a consistent inflationary scenario with only renormalizable superpotential interactions.

Abstract

We consider the extension of the supersymmetric Pati-Salam model introduced in order to solve the b-quark mass problem in supersymmetric theories with Yukawa unification, universal boundary conditions and mu>0. This model naturally leads to the new shifted and new smooth hybrid inflation scenarios, which, however, yield, in minimal supergravity, too large values of the spectral index n_s. We show that this problem can also be resolved within the same model by a two-stage inflationary scenario based only on renormalizable superpotential interactions. The first stage is of the standard and the second of the new smooth hybrid type. The cosmological scales exit the horizon during the first stage of inflation and acceptable n_s's can be achieved by restricting the number of e-foldings of our present horizon during this inflationary stage. The additional e-foldings needed for solving the horizon and flatness problems are naturally provided by the second stage of inflation. Monopoles are formed at the end of the first stage of inflation and are, subsequently, diluted by the second stage of inflation so that their density in the present universe is utterly negligible.