Spectral Distortions from Axion Monodromy Inflation

TL;DR

This paper predicts spectral distortions from axion monodromy inflation, showing they could be observed with future missions and could test the viability of this inflationary model.

Contribution

It computes spectral distortions for axion monodromy inflation, revealing oscillatory features and assessing their observability and implications for model falsifiability.

Findings

Spectral distortions are up to 10% larger than LCDM predictions.

Predicted signals are potentially observable with future missions like PIXIE.

Falsifying axion monodromy requires reducing observational errors by at least 100 times.

Abstract

With the advent of new missions to probe spectral distortions of the cosmic microwave background with unprecedented precision, the study of theoretical predictions of these signals becomes a promising avenue to test our description of the early Universe. Meanwhile, axion monodromy still offers a viable framework to describe cosmic inflation. In order to explore new constraints on inflationary models based on axion monodromy while aiming at falsifying this scenario, we compute the spectral distortions predicted by this model, revealing oscillatory features that are compatible with Planck data. Further, the predicted distortions are up to 10% larger than the signals obtained from the fiducial LCDM model and are observable in principle. However, contrasting with the predictions of the simplest power-law inflationary potentials challenges the falsifiability of axion monodromy as it would require to reduce at least 100 times the current forecast error of the PIXIE satellite, which shall be possible at some projected observational setups.