Hybrid inflation in high-scale supersymmetry

TL;DR

This paper explores how hybrid inflation models in high-scale supersymmetry can be stabilized by tadpole cancellation mechanisms, especially in no-scale supergravity, and discusses implications for dark radiation and spectral index consistency.

Contribution

It demonstrates that tadpole terms in hybrid inflation can be canceled using a supersymmetry breaking singlet, with automatic cancellation in no-scale supergravity, and analyzes the compatibility with moduli stabilization.

Findings

Tadpole cancellation is achievable with a supersymmetry breaking singlet.

No-scale supergravity naturally cancels the tadpole.

Dark radiation from volume modulus decay helps reconcile spectral index predictions.

Abstract

In hybrid inflation, the inflaton generically has a tadpole due to gravitational effects in supergravity, which significantly changes the inflaton dynamics in high-scale supersymmetry. We point out that the tadpole can be cancelled if there is a supersymmetry breaking singlet with gravitational couplings, and in particular, the cancellation is automatic in no-scale supergravity. We consider the LARGE volume scenario as a concrete example and discuss the compatibility between the hybrid inflation and the moduli stabilization. We also point out that the dark radiation generated by the overall volume modulus decay naturally relaxes a tension between the observed spectral index and the prediction of the hybrid inflation.