Observing nulling of primordial correlations via the 21 cm signal

Understand

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.