Multi-chaotic inflation with and without spectator field

TL;DR

This paper examines multi-field inflation models, especially double-inflaton scenarios with a spectator field, assessing their compatibility with recent observational data and identifying conditions to avoid fine-tuning.

Contribution

It demonstrates the viability of quadratic potential inflatons with a hierarchical mass spectrum and analyzes the impact of background trajectories on model predictions.

Findings

Quadratic potential inflatons can be viable with a specific mass hierarchy.

Spectator fields can be incorporated without fine-tuning.

Model predictions depend on the background trajectory in field space.

Abstract

Motivated by the result of Planck+BICEP/Keck recently released, we investigate the consistency of the multi-field inflation models in terms of the spectral index $n_s$ and the tensor-to-scalar ratio $r$. In this study, we focus on double-inflaton models with and without a spectator field. We find that inflaton with a quadratic potential can become viable when three fields with a specific hierarchical mass spectrum are realized such that two fields act as inflatons and the other one is the spectator. We also discuss the conditions to avoid the fine-tuning, by careful study of how the prediction depends on the background trajectory in the inflaton-field space.