A comprehensive investigation on the slowing down of cosmic acceleration

TL;DR

This paper investigates the potential slowing down of cosmic acceleration by analyzing theoretical models and observational data, finding that current evidence is inconclusive but suggests a possible slowdown, especially in non-flat universes.

Contribution

It provides a comprehensive analysis of the slowing down of cosmic acceleration using multiple models and observational datasets, highlighting the influence of spatial curvature and data selection.

Findings

Non-flat universe models favor slowing down of CA

SNLS3 data supports slowing down at 1σ confidence

Full CMB data more favor a slowing down of CA

Abstract

Shafieloo ea al. firstly proposed the possibility that the current cosmic acceleration (CA) is slowing down. However, this is rather counterintuitive because a slowing down CA cannot be accommodated in most mainstream cosmological models. In this work, by exploring the evolutionary trajectories of dark energy equation of state $w(z)$ and deceleration parameter $q(z)$, we present a comprehensive investigation on the slowing down of CA from both the theoretical and the observational sides. For the theoretical side, we study the impact of different $w(z)$ by using six parametrization models, and then discuss the effects of spatial curvature. For the observational side, we investigate the effects of different type Ia supernovae (SNe Ia), different baryon acoustic oscillation (BAO), and different cosmic microwave background (CMB) data, respectively. We find that (1) The evolution of CA are insensitive to the specific form of $w(z)$; in contrast, a non-flat Universe more favors a slowing down CA than a flat Universe. (2) SNLS3 SNe Ia datasets favor a slowing down CA at 1$\sigma$ confidence level, while JLA SNe Ia samples prefer an eternal CA; in contrast, the effects of different BAO data are negligible. (3) Compared with CMB distance prior data, full CMB data more favor a slowing down CA. (4) Due to the low significance, the slowing down of CA is still a theoretical possibility that cannot be confirmed by the current observations.