Building Models of Inflation in No-Scale Supergravity

TL;DR

This paper develops inflationary models within no-scale supergravity that replicate Starobinsky's predictions, exploring their structure, phenomenology, and potential to unify various cosmological and particle physics phenomena.

Contribution

It constructs no-scale supergravity inflation models matching Starobinsky's predictions and explores their structure, phenomenology, and unification potential.

Findings

Models reproduce Starobinsky's $n_s$ and $r$ predictions.

No-scale supergravity models relate closely to $R^2$ gravity.

Framework can incorporate GUTs and explain cosmological phenomena.

Abstract

After reviewing the motivations for cosmological inflation formulated in the formalism of supersymmetry, we argue that the appropriate framework is that of no-scale supergravity. We then show how to construct within this framework inflationary models whose predictions for the tilt in the spectrum of scalar perturbations, $n_s$, and the ratio, $r$, of tensor and scalar perturbations coincide with those of the $R + R^2$ model of inflation proposed by Starobinsky. A more detailed study of no-scale supergravity reveals a structure that is closely related to that of $R^2$ modifications of the minimal Einstein-Hilbert action for general relativity, opening avenues for constructing no-scale de Sitter and anti-de Sitter models by combining pairs of Minkowski models, as well as generalizations of the original no-scale Starobinsky models of inflation. We then discuss the phenomenology of no-scale models of inflation, including inflaton decay and reheating, and then the construction of explicit scenarios based on SU(5), SO(10) and string-motivated flipped SU(5)$\times$U(1) GUT models. The latter provides a possible model of almost everything below the Planck scale, including neutrino masses and oscillations, the cosmological baryon asymmetry and cold dark matter, as well as $n_s$ and $r$.