Cosmology of the string derived flipped $SU(5)$

TL;DR

This paper explores a string-derived supersymmetric flipped $SU(5)$ model's cosmology, demonstrating it can produce successful Starobinsky-like inflation using supergravity and specific superpotentials involving singlet fields.

Contribution

It introduces a novel cosmological scenario within a string-derived flipped $SU(5)$ model, showing how to achieve Starobinsky-type inflation with supergravity and string-inspired superpotentials.

Findings

Model accommodates successful Starobinsky inflation.

Inflation driven by singlet superfields with string-inspired superpotential.

Results are generalizable to similar string-derived models.

Abstract

We study the cosmology of a string derived supersymmetric flipped $SU(5)$ model in the context of free-fermionic heterotic constructions that allow full calculability of the effective supergravity in perturbation theory around the fermionic vacuum where all string moduli have fixed values. The model has 3 generations of chiral families and a Higgs sector leading to particle phenomenology consistent with low energy data, that has been extensively studied in the past. Here, we show that it can also accommodate a novel successful cosmology, based on the no-scale effective supergravity derived from string theory as well as an appropriate induced superpotential suppressed by five powers of the string scale. It utilises two gauge singlet chiral superfields present in the low energy spectrum: the inflaton $y$, identified as the superpartner of a state mixed with R-handed neutrinos, and the goldstino $z$ with a superpotential of the form $W_I=M_I z(y-\lambda y^2)$ (in supergravity units) where $\lambda$ is a dimensionless ${\cal O}\left(1\right)$ parameter and $M_I$ the mass scale of inflation generated at 5th order by the breaking of an anomalous $U(1)_A$ gauge symmetry, characteristic of heterotic string chiral vacua. The resulting scalar potential leads to Starobinsky type inflation. Our results can be easily generalised to a large class of models with similar properties.