arXiv 1805.030692018-05gr-qchep-th

恒定声速下团簇DBI暗能量模型的结构形成

Structure formation in clustering DBI dark energy model with constant sound speed

K. Fahimi, K. Karami, S. Asadzadeh, K. Rezazadeh

备注：: 13 pages, 9 figures
发表信息：: MNRAS 481, 2393 (2018)
DOI：: 10.1093/mnras/sty2416

摘要：

在暗能量的DBI非正则标量场模型的框架下，我们研究了线性和非线性区域中暗物质扰动的增长。在我们的DBI模型中，我们考虑了反德西特翘曲因子$f(ϕ)=f_0\, ϕ^{-4}$与常数$f_0>0$，并假设DBI暗能量是集群的，其声速$c_s$是恒定的。对于一个充满无压暗物质和DBI暗能量的空间平坦FRW宇宙，我们首先得到了背景量的演化行为。我们的结果表明，在我们的DBI模型中，宇宙从物质主导的时代开始，并在后期接近de Sitter宇宙，正如预期的那样。DBI势的行为也类似于幂律势$V(ϕ)\propto ϕ^n$。此外，我们使用伪牛顿形式获得的增长因子的暗物质扰动的线性制度。我们的结论是，对于较小的$c_s$（或$f_0$），暗物质的增长因子是较小的集群DBI模型相比，均匀的。在基于球形坍缩模型的非线性区域中，我们得到了线性密度$δ_c(z_c)$、维里密度$Δ_{\rm vir}(z_c)$、$ζ(z_c)$周围的密度以及坍缩区域的膨胀率$h_{\rm ta}(z)$ .我们指出，对于较小的$c_s$（或$\tilde{f}_0$），$δ_c(z_c)$，$Δ_{\rm vir}(z_c)$，$ζ(z_c)$和$h_{\rm ta}(z)$在非聚类DBI模型的值偏离$Λ$ CDM相比，聚类DBI。最后，借助球形坍缩参数，我们计算了给定质量以上的晕天体的相对数密度，并得出结论，对于高红移的高质量晕，聚类和均匀DBI模型之间的差异更为明显。

英文摘要：

Within the framework of DBI non-canonical scalar field model of dark energy, we study the growth of dark matter perturbations in the both linear and non-linear regimes. In our DBI model, we consider the anti-de Sitter warp factor $f(ϕ)=f_0\, ϕ^{-4}$ with constant $f_0>0$ and assume the DBI dark energy to be clustered and its sound speed $c_s$ to be constant. For a spatially flat FRW universe filled with pressureless dark matter and DBI dark energy, we first obtain the evolutionary behaviors of the background quantities. Our results show that in our DBI model, the universe starts from a matter dominated epoch and approaches to the de Sitter universe at late times, as expected. Also the DBI potential behaves like the power law one $V(ϕ)\propto ϕ^n$. In addition, we use the Pseudo-Newtonian formalism to obtain the growth factor of dark matter perturbations in the linear regime. We conclude that for smaller $c_s$ (or $f_0$), the growth factor of dark matter is smaller for clustering DBI model compared to the homogeneous one. In the following, in the non-linear regime based on the spherical collapse model, we obtain the linear overdensity $δ_c(z_c)$, the virial overdensity $Δ_{\rm vir}(z_c)$, overdensity at the turn around $ζ(z_c)$ and the rate of expansion of collapsed region $h_{\rm ta}(z)$. We point out that for the smaller $c_s$ (or $\tilde{f}_0$), the values of $δ_c(z_c)$, $Δ_{\rm vir}(z_c)$, $ζ(z_c)$ and $h_{\rm ta}(z)$ in non-clustering DBI models deviate more than the $Λ$CDM compared to the clustering DBI. Finally, with the help of spherical collapse parameters we calculated the relative number density of halo objects above a given mass and conclude that the differences between clustering and homogeneous DBI models are more pronounced for higher-mass halos at high redshift.

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