Semi-shifted hybrid inflation with B-L cosmic strings

TL;DR

This paper proposes a semi-shifted hybrid inflation model within supersymmetric Pati-Salam theory, compatible with cosmic string contributions and recent observational data, avoiding monopole formation and predicting specific spectral indices.

Contribution

It introduces a novel semi-shifted hybrid inflation scenario that aligns with cosmic string data and gauge unification constraints within supersymmetric models.

Findings

Cosmic strings contribute a small fraction to the CMB temperature spectrum.

Predicted spectral index n_s is around 1.0254 for best-fit string contribution.

Monopoles are not produced at the end of inflation.

Abstract

We discuss a new inflationary scenario which is realized within the extended supersymmetric Pati-Salam model which yields an acceptable b-quark mass for universal boundary conditions and mu>0 by modestly violating Yukawa unification and leads to new shifted, new smooth, or standard-smooth hybrid inflation. Inflation takes place along a "semi-shifted" classically flat direction on which the U(1)_{B-L} gauge group remains unbroken. After the end of inflation, U(1)_{B-L} breaks spontaneously and a network of local cosmic strings, which contribute a small amount to the curvature perturbation, is produced. We show that, in minimal supergravity, this "semi-shifted" inflationary scenario is compatible with a recent fit to data which uses field-theory simulations of a local string network. Taking into account the requirement of gauge unification, we find that, for spectral index n_s=1, the predicted fractional contribution f_{10} of strings to the temperature power spectrum at multipole l=10 is about 0.039. Also, for f_{10}=0.10, which is the best-fit value, we obtain that n_s is about 1.0254. Spectral indices lower than about 0.98 are excluded and blue spectra are slightly favored. Magnetic monopoles are not formed at the end of semi-shifted hybrid inflation.