Misc,

A comprehensive investigation on the slowing down of cosmic acceleration

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(Sep 11, 2015)

Abstract

In\~Shafieloo2009, Shafieloo, Sanhi and Starobinsky firstly proposed the possibility that the current cosmic acceleration (CA) is slowing down. This is rather counterintuitive, because a slowing down CA cannot be accommodated in almost all the 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 impacts 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 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. Moreover, we find that 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. In addition, compared with CMB distance prior data, full CMB data more favor a slowing down CA. Since the evolutionary behavior of CA depends on both the theoretical models and the observational data, the possibility of slowing down CA cannot be confirmed by current observations.

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