Probing features in inflaton potential and reionization history with future CMB space observations

TL;DR

This paper explores how future CMB polarization measurements, especially from CORE, can detect features in the primordial power spectrum caused by inflationary potential variations and distinguish them from reionization effects.

Contribution

It demonstrates that certain inflationary features can be constrained at high confidence levels with future CMB data and analyzes potential confusion with reionization signatures.

Findings

Features in the inflationary potential can be constrained at 3σ confidence with CORE.

Extended reionization history can mimic inflationary features, affecting their identification.

WWI models improve fit to Planck data, though not significantly.

Abstract

We consider the prospects of probing features in the primordial power spectrum with future Cosmic Microwave Background (CMB) polarization measurements. In the scope of the inflationary scenario, such features in the spectrum can be produced by local non-smooth pieces in an inflaton potential (smooth and quasi-flat in general) which in turn may originate from fast phase transitions during inflation in other quantum fields interacting with the inflaton. They can fit some outliers in the CMB temperature power spectrum which are unaddressed within the standard inflationary ${\mathrm{\Lambda}}$CDM model. We consider Wiggly Whipped Inflation (WWI) as a theoretical framework leading to improvements in the fit to the Planck 2015 temperature and polarization data in comparison with the standard inflationary models, although not at a statistically significant level. We show that some type of features in the potential within the WWI models, leading to oscillations in the primordial power spectrum that extend to intermediate and small scales can be constrained with high confidence (at 3$\sigma$ or higher confidence level) by an instrument as the Cosmic ORigins Explorer (CORE). In order to investigate the possible confusion between inflationary features and footprints from the reionization era, we consider an extended reionization history with monotonic increase of free electrons with decrease in redshift. We discuss the present constraints on this model of extended reionization and future predictions with CORE. We also project, to what extent, this extended reionization can create confusion in identifying inflationary features in the data.