Post-reionization HI 21-cm signal: A probe of negative cosmological constant

TL;DR

This paper explores how the post-reionization 21-cm signal can be used to probe a universe with a negative cosmological constant, providing forecasts for parameter constraints with future observations.

Contribution

It introduces a novel method using 21-cm power spectrum measurements to constrain negative cosmological constant models and dark energy parameters.

Findings

Negative cosmological constant with phantom dark energy is consistent with BAO data.

Forecasted constraints show potential to measure $\

21cm observations can significantly improve bounds on dark energy parameters.

Abstract

In this study, we investigate a cosmological model involving a negative cosmological constant (AdS vacua in the dark energy sector). We consider a quintessence field on top of a negative cosmological constant and study its impact on cosmological evolution and structure formation. We use the power spectrum of the redshifted HI 21 cm brightness temperature maps from the post-reionization epoch as a cosmological probe. The signature of baryon acoustic oscillations (BAO) on the multipoles of the power spectrum is used to extract measurements of the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$. The projected errors on these are then subsequently employed to forecast the constraints on the model parameters ($\Omega_\Lambda, w_0, w_a$) using Markov Chain Monte Carlo techniques. We find that a negative cosmological constant with a phantom dark energy equation of state (EoS) and a higher value of $H_0$ is viable from BAO distance measurements data derived from galaxy samples. We also find that BAO imprints on the 21cm power spectrum obtained from a futuristic SKA-mid like experiment yield a $1-\sigma$ error on a negative cosmological constant and the quintessence dark energy EoS parameters to be $\Omega_\Lambda=-1.030^{0.589}_{-1.712}$ and $w_0=-1.023^{0.043}_{-0.060}$, $w_a=-0.141^{0.478}_{-0.409}$ respectively.