Multi-chaotic inflation with and without spectator field

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.