Testing kinetically coupled inflation models with CMB distortions

TL;DR

This paper analyzes kinetically coupled inflation models' potential to produce detectable CMB spectral distortions, identifying five models that could be tested with future experiments like PIXIE, despite some tension with tensor mode constraints.

Contribution

It provides a model-oriented analysis of spectral distortion prospects for kinetically coupled inflation, highlighting five models with potential detectability in future CMB experiments.

Findings

Five models may generate detectable spectral distortions.

Kinetic coupling suppresses certain model parameters.

Tuned regions satisfy spectral tilt but not tensor mode constraints.

Abstract

Inflation scenarios kinetically coupled with the Einstein tensor have been widely studied. They can be consistent with current observational data. Future experiments on the measurement on CMB distortions will potentially extend information about the scalar spectrum to small scales $1 \Mpc^{-1} \lesssim k \lesssim 2 \times 10^4 \Mpc^{-1}$. By taking the sensitivity of the PIXIE experiment as the criterion, we perform a model-oriented analysis of the observational prospects of spectral distortions for kinetically coupled inflation. There are five models that possibly generate a detectable level of distortions, among the 49 single-field inflation models listed in Ref. \cite{Martin2013a}. These models are: hybrid inflation in the valley (VHI), non-canonical K\"{a}hler inflation (NCKI), generalized MSSM inflation (GMSSMI), generalized renormalization point inflation (GRIPI), and running-mass inflation (RMI). Each of these models can satisfy the Planck constraints on spectral tilt and lead to increase power on scales relevant for CMB distortions in a tuned region of their parameter space. The existence of kinetic coupling suppresses the value of the model parameters with mass dimension for VHI, GMSSMI, and GRIPI, such that these three models can be in agreement with their theoretical considerations. However, the tuned regions for all these models fail to satisfy the constraints on tensor modes.