Probing isocurvature perturbations with 21-cm global signal in the light of HERA result

TL;DR

This paper demonstrates that the 21-cm global signal, combined with HERA astrophysical constraints, can effectively probe isocurvature perturbations, especially those with blue-tilted spectra, reducing astrophysical uncertainties.

Contribution

It introduces a method to infer isocurvature perturbation properties from 21-cm signals using HERA data to mitigate astrophysical uncertainties.

Findings

21-cm global signal can probe isocurvature perturbations

HERA results help constrain astrophysical parameters

Spectral tilt of isocurvature perturbations can be inferred

Abstract

We argue that the 21-cm global signal can be a powerful probe of isocurvature perturbations, particularly for the ones with blue-tilted spectra. Although the 21-cm global signal is much affected by astrophysical processes, which give some uncertainties when cosmological models are investigated, recent results from HERA have constrained several astrophysical parameters, whose information can reduce the ambiguities originating from astrophysics. We show that the size and spectral tilt of isocurvature perturbations can be well inferred from the 21-cm global signal once the information on astrophysics from the HERA results is taken into account.