Observing nulling of primordial correlations via the 21 cm signal

TL;DR

This paper explores how a phase of ultra-slow-roll inflation can cause nulls in primordial correlations, which could be detected through the 21 cm signal from the Dark Ages, offering insights into early universe physics.

Contribution

It demonstrates that ultra-slow-roll inflation can produce nulls in primordial correlations at specific scales and assesses the detectability of these nulls via future 21 cm observations.

Findings

Nulls in primordial correlations can occur at specific wavenumbers due to ultra-slow-roll.

Future 21 cm observations could detect these nulls in power spectra and bi-spectra.

Detection of nulls would provide evidence for particular inflationary dynamics.

Abstract

The 21cm line emitted by neutral hydrogen (HI) during the Dark Ages carries imprints of pristine primordial correlations. In models of inflation driven by a single, canonical scalar field, we show that a phase of ultra-slow-roll can lead to a null in all the primordial correlations at a specific wavenumber $k_\textrm{dip}$. We consider scenarios wherein the null in the correlations occurs over wavenumbers $1 \lesssim k_\textrm{dip} \lesssim 10\,\mathrm{Mpc}^{-1}$, and examine the prospects of detecting such a damping in the HI signal due to the nulls at the level of power and bi-spectra in future observational missions.