Post-reionization H i 21-cm signal: a probe of negative cosmological constant

Abstract

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 H i 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 DA(z) and the Hubble parameter H(z). The projected errors on these are then subsequently employed to forecast the constraints on the model parameters ($H_0, \Omega _{m}, \Omega _\Lambda , w_0, w_a$) 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 H0 is viable from BAO distance measurements data derived from galaxy samples. We also find that BAO imprints on the 21-cm power spectrum obtained from a futuristic SKA-mid like experiment yield a 1σ 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.