The rate of structure formation in the Universe is different in homogeneous and clustered dark energy models. The degree of dark energy clustering depends on the magnitude of its effective sound speed $c^{2}_{\rm eff}$ and for $c_{\rm eff}=0$ dark energy clusters in a similar fashion to dark matter while for $c_{\rm eff}=1$ it stays (approximately) homogeneous. In this paper we consider two distinct equations of state for the dark energy component, $w_{\rm d}=const$ and $w_{\rm d}=w_0+w_1\left(\frac{z}{1+z}\right)$ with $c_{\rm eff}$ as a free parameter and we try to constrain the dark energy effective sound speed using current available data including SnIa, Baryon Acoustic Oscillation, CMB shift parameter ({\em Planck} and {\em WMAP}), Hubble parameter, Big Bang Nucleosynthesis and the growth rate of structures $fσ_{8}(z)$. At first we derive the most general form of the equations governing dark matter and dark energy clustering under the assumption that $c_{\rm eff}=const$.
Finally, performing an overall likelihood analysis we find that the likelihood function peaks at $c_{\rm eff}=0$, however the dark energy sound speed is degenerate with respect to the cosmological parameters, namely $Ω_{\rm m}$ and $w_{\rm d}$.
Cosmological hydrodynamical simulations of clustering dark energy with Nefertiti
The University of Tokyo（东京大学）；Observatoire de Paris, Université PSL, Sorbonne Université, CNRS（巴黎天文台，PSL大学，索邦大学，法国国家科学研究中心）；Université Paris-Cité（巴黎西岱大学）；Max–Planck–Institut für Astrophysik（马克斯·普朗克天体物理研究所）；École Polytechnique（巴黎综合理工学院）
Cosmological perturbations and clustering mechanisms in multifield dark energy
Bu-Ali Sina University（布阿利西纳大学）；Instituto de Física Teórica (IFT) UAM-CSIC（马德里自治大学-西班牙高等科学研究委员会理论物理研究所）；Department of Physics, Case Western Reserve University（凯斯西储大学物理系）；Imperial College London（帝国理工学院）
Understanding the influence of dark energy on the formation of structures is currently a major challenge in Cosmology, since it can distinguish otherwise degenerated viable models. In this work we consider the Top-Hat Spherical-Collapse (SC) model with dark energy, which can partially (or totally) cluster, according to a free parameter $γ$. The {\it lack of} energy conservation has to be taken into account accordingly, as we will show. We determine characteristic quantities for the SC model, such as the critical contrast density and radius evolution, with particular emphasis on their dependenc…
One of the non-canonical descriptions of scalar field dark energy is the tachyon. The present work is devoted to study the dynamics of dark matter overdensity in a conformally coupled tachyon field dark energy model. The model is tuned to mimic the $Λ$CDM cosmology at background level. The semi-analytic spherical collapse model of dark matter overdensity is adopted to study the nonlinear evolution. The effects of non-minimal coupling in the energy budget on the clustering of dark matter is investigated. It is observed that the growth rate of matter overdensity is higher in presence of the non-…
Universal clustering of dark matter in phase space
我们最近介绍了一种新的统计措施的暗物质在相空间中的聚类，粒子相空间平均密度（$P^2SAD$）。在两篇论文系列中，我们研究了银河大小的宝瓶座晕中$P^2SAD$的结构，构建了一个物理模型来描述它，并说明了它作为预测暗物质晕纳米结构敏感信号的强大工具的潜力。在这封信中，我们报告了一个显着的普适性的集群的暗物质在相空间中测量的$P^2SAD$内的subhaloes的主机晕跨越不同的环境覆盖范围从矮大小到集群大小的晕（$10^{10}-10^{15}$ M $_\odot$）。仿真结果表明，$P^2SAD$的普适性持有超过7个数量级，在一个2D相空间，覆盖超过3个数量级的距离/速度，与一个简单的函数形式，可以描述我们的模型。证明了$P^2SAD$的普适性，我们可以精确地预测小尺度下暗物质的非线性功率谱，一直到冷暗物质粒子的退耦质量极限。作为一个应用，我们计算的subhalo助推的湮灭暗物质在很宽的范围内的主机晕质量。
Predicting the spatial distribution of objects as a function of cosmology is an essential ingredient for the exploitation of future galaxy surveys. In this paper we show that a specially-designed suite of gravity-only simulations together with cosmology-rescaling algorithms can provide the clustering of dark matter, haloes, and subhaloes with high precision. Specifically, with only 3 $N$-body simulations we obtain the power spectrum of dark matter at $z=0$ and $z=1$ to better than 3\% precision for essentially all currently viable values of 8 cosmological parameters, including massive neutrino…
We review dark energy models which can present non-negligible fluctuations on scales smaller than Hubble radius. Both linear and nonlinear evolutions of dark energy fluctuations are discussed. The linear evolution has a well-established framework, based on linear perturbation theory in General Relativity, and is well studied and implemented in numerical codes. We highlight the main results from linear theory to explain how dark energy perturbations become important on the scales of interest for structure formation. Next, we review some attempts to understand the impact of clustering dark energ…
We extend the analysis of Pace et al., JCAP, 2019, 060, by considering the virialization process in the extended spherical collapse model for clustering dark-energy models, i.e., accounting for dark-energy fluctuations. Differently from the standard approach, here virialization is naturally achieved by properly modelling deviations from sphericity due to shear and rotation induced by tidal interactions. We investigate the time evolution of the virial overdensity $Δ_\mathrm{vir}$ in seven clustering dynamical dark energy models and compare the results to the $Λ$CDM model and to the correspondin…
Interacting dark energy models have been proposed as attractive alternatives to $Λ$CDM. Forthcoming Stage-IV galaxy clustering surveys will constrain these models, but they require accurate modelling of the galaxy power spectrum multipoles on mildly non-linear scales. In this work we consider a dark scattering model with a simple 1-parameter extension to $w$CDM - adding only $A$, which describes a pure momentum exchange between dark energy and dark matter. We then provide a comprehensive comparison of three approaches of modeling non-linearities, while including the effects of this dark sector…
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements and the strong power of normalized growth rate on constraining dark energy
Small scale clustering of late forming dark matter
我们对后期形成的暗物质（LFDM）场景中物质的非线性聚集进行了研究，其中暗物质是由非最小耦合的标量场从辐射到无碰撞物质的转变产生的。该模型的一个显著特点是在小尺度下线性物质功率谱中存在阻尼振荡截止。我们使用一套高分辨率的N体模拟来研究LFDM在非线性物质功率谱、晕质量和速度函数以及晕密度分布上的印记。该模型在很大程度上满足高红移物质的功率谱限制莱曼- $α$森林测量，而它预测抑制丰度的低质量晕（$\sim 10^{9}-10^{10}$ h $^{-1}$ M $_\odot$）在所有的红移相比，香草$Λ$ CDM模型。对LFDM晕速度函数的分析表明，与$Λ$ CDM预测相比，LFDM晕速度函数与观测到的低速星系在局部体积中的丰度更接近。质量为$M\gtrsim 10^{11}$ h $^{-1}$ M $_\odot$的晕显示出密度分布与$Λ$ CDM预期值的微小偏差，而质量较小的晕密度较低，这与它们比$Λ$ CDM对应物晚形成的事实相一致。
Clustering properties of galaxies selected in stellar mass: Breaking down the link between luminous and dark matter in massive galaxies from z=0 to z=2
Probing the sound speed and clustering of dark energy
University of Science and Technology of China（中国科学技术大学）；CAS Key Laboratory for Research in Galaxies and Cosmology, School of Astronomy and Space Science, University of Science and Technology of China（中国科学院星系与宇宙学重点实验室，中国科学技术大学天文与空间科学学院）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学 Kavli宇宙粒子物理联合研究所（WPI），UTIAS）；Lanzhou University（兰州大学）；National Observatory of Athens（雅典国家天文台）
