Constraints on TeV-scale hybrid inflation and comments on non-hybrid alternatives

TL;DR

This paper examines the constraints on TeV-scale hybrid inflation models, highlighting the challenges posed by loop corrections and suggesting that alternative inflation scenarios like new or thermal inflation are more viable at low energies.

Contribution

It provides a detailed analysis of the limitations of TeV-scale hybrid inflation and discusses the viability of alternative inflation models at low energy scales.

Findings

Hybrid inflation at TeV scale faces significant constraints due to loop corrections.

Inflaton and trigger fields must be very large ($>10^9$ GeV) after inflation.

New and thermal inflation are viable alternatives at low energy scales.

Abstract

During hybrid inflation, the slowly-rolling inflaton field has a significant coupling to the trigger field which is responsible for most of the potential. Barring a fine-tuned accidental cancellation, this coupling induces a minimal one-loop contribution to the inflaton potential. The requirement that this contribution be not too large constrains a wide class of hybrid inflation models. Assuming that the inflaton perturbation generates structure in the Universe, the inflaton field and/or the trigger field after inflation have to be bigger than $10^9\GeV$. This and other results make hybrid inflation at or below the TeV scale problematical. (There is no problem with hybrid inflation at the high energy scales normally considered.) `New' and thermal inflation seem to be viable alternatives for inflation at or below the TeV scale, including the case that quantum gravity is at the TeV scale. In any case, supersymmetry is needed required during inflation, in order to protect a scalar mass.