Revisiting a non-parametric reconstruction of the deceleration parameter from combined background and the growth rate data

The cosmic deceleration parameter q has been reconstructed in a non-parametric way using various combinations of recent observational datasets. The Pantheon compilation of the Supernova (SN) distance modulus data, the Cosmic Chronometer (CC) measurements of the Hubble parameter including the full systematics and the Baryon Acoustic Oscillation (BAO) data have been considered in this work. The redshift z(t), where the transition from a past decelerated to a late-time accelerated phase of evolution occurs, is estimated from the reconstructed q. The possible effect of a non-zero spatial curvature from the Planck 2020 estimate is checked. The outcome of including different H-0 measurements from recent Planck 2020 and Riess 2021 probes having a maximum discrepancy at the 4.2 sigma level, is investigated. Results indicate that the transition from a past decelerated phase to the late-time accelerated phase occurs within the redshift range 0.5 < z < 1. The reconstructed q is observed to have a non-monotonic evolution in case of the combined CC and SN data for z > 1, which becomes oscillatory on introducing the BAO data. To investigate the effect of matter perturbations, the growth rate data from the Redshift-Space Distortions (RSD) are utilized in reconstructing q. Using the Omicron m(z) diagnostic, we draw inferences on the validity of Lambda CDM as a consistency check. The Lambda CDM model is well consistent and included at the 2 sigma level in the domain of all the reconstructions. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The cosmic deceleration parameter q has been reconstructed using non-parametric methods and various observational datasets. The transition from a past decelerated phase to a late-time accelerated phase occurs within the redshift range 0.5 < z < 1. The evolution of q is found to be non-monotonic and oscillatory when considering different H-0 measurements and introducing Baryon Acoustic Oscillation (BAO) data.