Shift Symmetry and Higgs Inflation in Supergravity with Observable Gravitational Waves

TL;DR

This paper presents a supergravity-based Higgs inflation model with shift symmetry that predicts observable gravitational waves and aligns with current cosmological data, using a novel chaotic inflation scenario driven by GUT-scale Higgs fields.

Contribution

It introduces a new supergravity inflation model utilizing shift symmetry and Higgs fields, achieving subplanckian inflation with observable gravitational waves and consistent with unitarity and defect constraints.

Findings

Inflation occurs with subplanckian inflaton values.

Model predicts observable gravitational waves.

Inflaton mass range is (3.7-8.1)×10^10 GeV.

Abstract

We demonstrate how to realize within supergravity a novel chaotic-type inflationary scenario driven by the radial parts of a conjugate pair of Higgs superfields causing the spontaneous breaking of a grand unified gauge symmetry at a scale assuming the value of the supersymmetric grand unification scale. The superpotential is uniquely determined at the renormalizable level by the gauge symmetry and a continuous R symmetry. We select two types of Kahler potentials, which respect these symmetries as well as an approximate shift symmetry. In particular, they include in a logarithm a dominant shift-symmetric term proportional to a parameter c- together with a small term violating this symmetry and characterized by a parameter c+. In both cases, imposing a lower bound on c-, inflation can be attained with subplanckian values of the original inflaton, while the corresponding effective theory respects perturbative unitarity for r+-=c+/c-<1. These inflationary models do not lead to overproduction of cosmic defects, are largely independent of the one-loop radiative corrections and accommodate, for natural values of r+-, observable gravitational waves consistently with all the current observational data. The inflaton mass is mostly confined in the range (3.7-8.1)x10^10 GeV.