Constrained inflaton due to a complex scalar

TL;DR

This paper explores a complex scalar field model for inflation where the inflaton follows a spiral trajectory, enabling sub-Planckian inflation with observable predictions similar to monomial potentials, and connects it to neutrino mass models.

Contribution

It introduces a constrained inflaton model with a spiral-like potential allowing sub-Planckian inflation and links it to radiative neutrino mass models.

Findings

Sub-Planckian inflaton can produce sufficient e-foldings.

Scalar spectral index and tensor-to-scalar ratio match monomial inflation predictions in a special limit.

Model parameters can be tuned to fit observational data.

Abstract

We reexamine inflation due to a constrained inflaton in the model of a complex scalar. Inflaton evolves along a spiral-like valley of special scalar potential in the scalar field space just like single field inflation. Sub-Planckian inflaton can induce sufficient $e$-foldings because of a long slow-roll path. In a special limit, the scalar spectral index and the tensor-to-scalar ratio has equivalent expressions to the inflation with monomial potential $\varphi^n$. The favorable values for them could be obtained by varying parameters in the potential. This model could be embedded in a certain radiative neutrino mass model.