arXiv 1706.025372017-06-07astro-ph.COgr-qc

使用PADE参数化对暗能量的约束

Constraints to dark energy using PADE parameterisations

Mehdi Rezaei, Mohammad Malekjani, Spyros Basilakos, Ahmad Mehrabi, David F. Mota

备注：: 15 pages, 6 figures and 5 tables. Accepted in ApJ

摘要：

我们把约束暗能量属性使用PADE参数化，并比较它与相同的约束使用Chevalier-Polarski-Linder（CPL）和$Λ$ CDM，在背景和扰动水平。通过对PADE展开的数学处理，导出了模型的暗能量状态方程参数。与CPL参数化不同，PADE近似提供了不同形式的状态方程参数，从而避免了将来的发散。最初，我们进行了似然分析，以便仅使用背景扩展数据对模型参数进行约束，我们发现所有参数化都是相互一致的。然后，结合扩展和增长率的数据，我们测试的PADE参数化的可行性，并比较他们与CPL和$Λ$ CDM模型分别。具体地说，我们发现，目前的PADE参数化的增长率是低于$Λ$ CDM模型在低红移，而在高红移的差异可以忽略不计。在这方面，我们提供了第一次在PADE宇宙学线性物质扰动的增长指数。考虑到暗能量是均匀的，我们恢复了众所周知的增长指数的渐近值，即$γ_{\infty}=\frac{3(w_{\infty}-1)}{6w_{\infty}-5}$，而在集群的暗能量的情况下，我们得到$γ_{\infty}\simeq \frac{3w_{\infty}(3w_{\infty}-5)}{(6w_{\infty}-5)(3w_{\infty}-1)}$。最后，我们推广了增长指数分析的情况下，$γ$是允许的红移变化，我们发现，$γ(z)$的形式在PADE参数化的CPL和$Λ$ CDM宇宙学分别延伸。

英文摘要：

We put constraints on dark energy properties using the PADE parameterisation, and compare it to the same constraints using Chevalier-Polarski-Linder (CPL) and $Λ$CDM, at both the background and the perturbation levels. The dark energy equation of state parameter of the models is derived following the mathematical treatment of PADE expansion. Unlike CPL parameterisation, the PADE approximation provides different forms of the equation of state parameter which avoid the divergence in the far future. Initially, we perform a likelihood analysis in order to put constraints on the model parameters using solely background expansion data and we find that all parameterisations are consistent with each other. Then, combining the expansion and the growth rate data we test the viability of PADE parameterisations and compare them with CPL and $Λ$CDM models respectively. Specifically, we find that the growth rate of the current PADE parameterisations is lower than $Λ$CDM model at low redshifts, while the differences among the models are negligible at high redshifts. In this context, we provide for the first time growth index of linear matter perturbations in PADE cosmologies. Considering that dark energy is homogeneous we recover the well known asymptotic value of the growth index, namely $γ_{\infty}=\frac{3(w_{\infty}-1)}{6w_{\infty}-5}$, while in the case of clustered dark energy we obtain $γ_{\infty}\simeq \frac{3w_{\infty}(3w_{\infty}-5)}{(6w_{\infty}-5)(3w_{\infty}-1)}$. Finally, we generalize the growth index analysis in the case where $γ$ is allowed to vary with redshift and we find that the form of $γ(z)$ in PADE parameterisation extends that of the CPL and $Λ$CDM cosmologies respectively.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

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