SUGRA Hybrid Inflation with Shift Symmetry

TL;DR

This paper introduces a supergravity hybrid inflation model employing shift symmetry to solve the eta-problem, ensuring a flat potential at tree level and aligning spectral index predictions with observational data.

Contribution

It presents a novel class of SUGRA hybrid inflation models using shift symmetry to maintain flatness and control couplings, addressing key issues in inflation theory.

Findings

Achieves a flat inflaton potential at tree level via shift symmetry.

Predicts spectral index consistent with WMAP observations (~0.96).

Avoids dangerous couplings between inflaton and moduli sectors.

Abstract

We propose a solution to the eta-problem in supergravity (SUGRA) hybrid inflation using a Nambu-Goldstone-like shift symmetry within a new class of models. The flatness of the tree-level inflaton potential is ensured by shift symmetry invariance of the Kaehler potential, while a small symmetry breaking term in the superpotential gives rise to a slope of the potential at loop-level. In the proposed class of inflation models, potentially dangerous couplings between the inflaton and the moduli sector are avoided. We also discuss under which conditions the predicted spectral index can be in agreement with the best-fit-value of the latest WMAP observation n_s ~ 0.96, corresponding to a hilltop-type inflaton potential at loop-level.