From Hybrid to Quadratic Inflation With High-Scale Supersymmetry Breaking

TL;DR

This paper proposes a supergravity-based inflation model that transitions from hybrid to quadratic inflation, predicting observable gravitational waves consistent with BICEP2 results, and involves high-scale supersymmetry breaking and gauge symmetry breaking near the GUT scale.

Contribution

It introduces a novel supergravity inflation model incorporating high-scale supersymmetry breaking and shift symmetry, aligning hybrid and quadratic inflation features.

Findings

Predicts tensor-to-scalar ratio r ~ 0.14

Achieves scalar spectral index ns ~ 0.964

Connects inflation end with gauge symmetry breaking at GUT scale

Abstract

Motivated by the reported discovery of inflationary gravity waves by the BICEP2 experiment, we propose an inflationary scenario in supergravity, based on the standard superpotential used in hybrid inflation. The new model yields a tensor-to-scalar ratio r ~ 0.14 and scalar spectral index ns ~ 0.964, corresponding to quadratic (chaotic) inflation. The important new ingredients are the high-scale, (1.6-10) x 10^13 GeV, soft supersymmetry breaking mass for the gauge singlet inflaton field and a shift symmetry imposed on the K\"ahler potential. The end of inflation is accompanied, as in the earlier hybrid inflation models, by the breaking of a gauge symmetry at (1.2-7.1) x 10^16 GeV, comparable to the grand-unification scale.