When Did Cosmic Acceleration Start ?

TL;DR

This paper precisely constrains the epoch of cosmic acceleration onset and dark energy domination using multiple datasets, revealing that acceleration began around redshift 0.76 to 0.81, depending on the model.

Contribution

It provides updated constraints on the timing of cosmic acceleration and dark energy dominance across different cosmological models using combined observational data.

Findings

Acceleration started around redshift 0.76-0.81.

Dark energy domination occurred at redshift ~0.48-0.80.

Constraints vary significantly with model assumptions.

Abstract

A precise determination, and comparison, of the epoch of the onset of cosmic acceleration, at redshift z_acc, and of dark energy domination, at z_eq, provides an interesting measure with which to parameterize dark energy models. By combining several cosmological datasets we place constraints on the redshift and age of cosmological acceleration. For a Lambda-CDM model, we find the constraint z_acc=0.76\pm0.10 at 95% c.l., occurring 6.7\pm0.4 Gyrs ago. Allowing a constant equation of state but different from -1 changes the constraints to z_acc=0.81\pm0.12 (6.9\pm0.5 Gyrs ago) and z_eq=0.48\pm0.14(4.9\pm0.9 Gyrs ago), while dynamical models markedly increase the error on the constraints with z_acc=0.81\pm0.30 (6.8\pm1.4 Gyrs ago) and z_eq=0.44\pm0.20 (4.5\pm1.0 Gyrs ago). Unified dark energy models as Silent Quartessence yield: z_acc=0.80\pm0.16 (6.8\pm0.6 Gyrs ago).