Drifting Oscillations in Axion Monodromy

TL;DR

This paper investigates the impact of drifting oscillations in the primordial power spectrum within axion monodromy inflation, providing templates for data analysis and performing preliminary searches in Planck data.

Contribution

It introduces models and templates that account for moduli-induced drifting oscillations in the power spectrum, enhancing the analysis of inflationary signals in cosmological data.

Findings

Drifting modulations can significantly affect the oscillation patterns in the power spectrum.

Templates incorporating drift parameters improve detection prospects for high-frequency oscillations.

Preliminary analysis of Planck data shows potential for identifying drifting oscillations.

Abstract

We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.