A kinematical approach to dark energy studies
A kinematical approach to dark energy studies
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DOI：
10.1111/j.1365-2966.2006.11419.x
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发表时间：
2006-05
影响因子：
4.8
通讯作者：
D. Rapetti;S. Allen;M. Amin;R. Blandford
中科院分区：
文献类型：
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作者：
D. Rapetti;S. Allen;M. Amin;R. Blandford
我们提出并采用了一种新的运动学方法来宇宙学的“暗能量”的研究。我们根据尺度因子a（t）对宇宙时间t的无量纲二阶和三阶导数，即减速参数q0和宇宙加加速度参数j（t）的当前值，构建模型。这种参数化的一个优雅的特征是，所有的冷暗物质（CDM）模型都有j（t）= 1（常数），这有利于简单的测试偏离CDM范式。将我们的模型应用到三组最佳的红移独立距离测量，从Ia型超新星和X射线团簇气体质量分数测量，我们获得了明确的统计证据，从减速到加速阶段的后期过渡。对于具有常数加加速度的平坦模型，j（t）= j，我们测量q0 =− 0.81 ± 0.14和j = 2.16 + 0.81 −0.75，结果在1σ置信水平下与CDM一致。对相同数据进行标准的“动力学”分析，采用弗里德曼方程，并将暗能量建模为具有状态方程参数w（常数）的流体，得到m = 0.306 + 0.042 −0.040和w =− 1.15 + 0.14 −0.18，在1σ水平上也与CDM一致。与动力学分析相比，运动学方法使用不同的模型集，并采用最少的先验信息，独立于任何特定的重力理论。因此，用这种新方法获得的结果提供了重要的额外信息，我们认为，在未来的暗能量研究中，在可能的情况下，运动学和动力学技术都应该采用。我们的研究结果提供了进一步有趣的支持concordanceCDM范式。
We present and employ a new kinematical approach to cosmological 'dark energy' studies. We construct models in terms of the dimensionless second and third derivatives of the scalefactor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q0 and the cosmic jerk parameter, j(t). An elegant feature of this parametrization is that all � cold dark matter (� CDM) models have j(t) = 1 (constant), which facilitates simple tests for departures from theCDM paradigm. Applying our model to the three best available sets of redshift-independent distance measurements, from Type Ia supernova and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late-time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t) = j, we measure q0 =− 0.81 ± 0.14 and j = 2.16 +0.81 −0.75 , results that are consistent withCDM at about the 1σ confidence level. A standard 'dynamical' analysis of the same data, employing the Friedmann equations and modelling the dark energy as a fluid with an equation-of-state parameter, w (constant), givesm = 0.306 +0.042 −0.040 and w =− 1.15 +0.14 −0.18, also consistent with � CDM at about the 1σ level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible. Our results provide further interesting support for the concordanceCDM paradigm.