Mixed Inflaton and Spectator Field Models: CMB constraints and $\mu$ distortion

TL;DR

This paper investigates mixed inflaton and spectator field models for primordial density fluctuations, using CMB data to constrain these models and predict spectral $d$ distortion, highlighting the potential of future measurements to test such models.

Contribution

It provides the first comprehensive analysis of CMB constraints on mixed inflaton and spectator field models, including predictions for spectral $d$ distortion.

Findings

Mixed models predict broader $d$ distortion distribution.

Standard single-field inflaton predicts $d \u2248 10^{-8}$.

Future $d$ measurements can test mixed models.

Abstract

We discuss mixed inflaton and spectator field models where both the fields are responsible for the observed density fluctuations. We use the current CMB data to constrain both the general mixed model as well as some specific representative scenarios, and collate the results with the model predictions for the CMB spectral $\mu$ distortion. We find the posterior distribution of $\mu$ using MCMC chains and demonstrate that the standard single-field inflaton model typically predicts $\mu \sim 10^{-8}$ with a relatively narrow distribution, whereas for the mixed models, the distribution turns out to be much broader, and $\mu$ could be larger by almost an order of magnitude. Hence future experiments of $\mu$ distortion could provide a tool for the critical testing of the mixed source models of the primordial perturbation.