宇宙加速减慢的综合考察
A comprehensive investigation on the slowing down of cosmic acceleration
摘要：
Shafieloo等人首先提出了当前宇宙加速（CA）正在减慢的可能性。然而，这是相当违反直觉的，因为在大多数主流的宇宙学模型中，一个减速的CA是不可能被容纳的。本文通过对暗能量状态方程$w(z)$和减速参数$q(z)$的演化轨迹的研究，从理论和观测两个方面对CA的慢化进行了全面的研究。在理论方面，我们使用六个参数化模型来研究不同$w(z)$的影响，然后讨论空间曲率的影响。在观测方面，我们分别研究了不同Ia型超新星（SNe Ia）、不同的重子声学振荡（BAO）和不同的宇宙微波背景（CMB）数据的影响。我们发现：（1）CA的演化对$w(z)$的具体形式不敏感;相比之下，非平坦宇宙比平坦宇宙更有利于CA的减慢。(2)SNLS 3 SNe Ia数据集在1 $σ$置信水平下有利于CA减慢，而JLA SNe Ia样本更喜欢永恒CA;相反，不同BAO数据的影响可以忽略不计。(3)与CMB距离先验数据相比，完整CMB数据更有利于减缓CA。(4)由于显著性较低，CA的减慢仍然是一种理论上的可能性，无法被目前的观测所证实。
英文摘要：
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$σ$ 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.
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