We consider the possibility that the universe is made of a single dark fluid described by a logotropic equation of state $P=A\ln(ρ/ρ_*)$, where $ρ$ is the rest-mass density, $ρ_*$ is a reference density, and $A$ is the logotropic temperature. The energy density $ε$ is the sum of two terms: a rest-mass energy term $ρc^2$ that mimics dark matter and an internal energy term $u(ρ)=-P(ρ)-A$ that mimics dark energy. This decomposition leads to a natural, and physical, unification of dark matter and dark energy, and elucidates their mysterious nature. The logotropic model depends on a single parameter $B=A/ρ_Λc^2$ where $ρ_Λ$ is the cosmological density. For $B=0$, we recover the $Λ$CDM model. Using cosmological constraints, we find that $0\le B\le 0.09425$. We consider the possibility that dark matter halos are described by the same logotropic equation of state. When $B>0$, pressure gradients prevent gravitational collapse and provide halo density cores instead of cuspy density profiles, in agreement with the observations. The universal rotation curve of logotropic dark matter halos is consistent with the observational Burkert profile up to the halo radius. Interestingly, if we assume that all the dark matter halos have the same logotropic temperature $B$, we find that their surface density $Σ=ρ_0 r_h$ is constant. This result is in agreement with the observations where it is found that $Σ_0=141\, M_{\odot}/{\rm pc}^2$ for dark matter halos differing by several orders of magnitude in size. Using this observational result, we obtain $B=3.53\times 10^{-3}$. Assuming that $ρ_*=ρ_P$, where $ρ_P$ is the Planck density, we predict $B=3.53\times 10^{-3}$, in perfect agreement with the value obtained from the observations.
Extended logotropic fluids as unified dark energy models
我们在这里研究扩展类的logotropic流体\textit{unified dark energy models}。在Anton-Schmidt方案的假设下，我们认为宇宙服从单一流体，其压力通过对数状态方程演化。这个结果与各向同性应力下的晶体类似。因此，我们调查的热力学和动力学的后果整合的声速，以获得压力的密度，导致扩展版本的Anton-Schmidt宇宙流体。在这幅图中，我们得到了在红外区域扩展Anton-Schmidt压力的重要结果。低能情况与宇宙在没有任何宇宙学常数的情况下加速有关。因此，我们推导出我们的流体的拉格朗日$\mathcal{L}=\mathcal{L}(X)$的有效表示，仅取决于动力学项$X$。我们分析了相对论和非相对论的限制。在非相对论极限下，我们用密度$ρ$和标量场$\vartheta$构造了哈密顿量和拉格朗日量，而在相对论极限下，我们找不到拉格朗日量的解析表达式，因此，在无旋理想流体的假设下，我们得到了作为$ρ$的函数的势.我们证明了该模型是\emph{logotropic dark energy models}的自然推广。最后，我们分析了一类带有一个额外参数$β$的广义Chaubergin气体模型。有趣的是，我们发现，这种情况下的拉格朗日和纯logotropic一个重合的非相对论制度。
We have considered a spatially flat, homogeneous and isotropic FLRW Universe filled with a single fluid, known as logotropic dark fluid (LDF), whose pressure evolves through a logarithmic equation of state. We use the recent Pantheon SNIa and cosmic chronometer datasets to constrain the parameters of this model, the present fraction of dark matter $Ω_{m0}$ and the Hubble constant $H_0$. We find that the mean values of these parameters are $Ω_{m0}=0.288\pm 0.012$ and $H_{0}=69.652\pm 1.698~{\rm km/s/Mpc}$ at the $1σ$ CL. We also find that the LDF model shows a smooth transition from the deceler…
The logotropic model [P.H. Chavanis, Eur. Phys. J. Plus {\bf 130}, 130 (2015)] may be an interesting alternative to the $Λ$CDM model. It is able to account for the present accelerating expansion of the universe while solving at the same time the core-cusp problem of the CDM model. In the logotropic model, there is a single dark fluid. Its rest-mass plays the role of dark matter and its internal energy plays the role of dark energy. We highlight two remarkable predictions of the logotropic model. It yields cored dark matter halos with a universal surface density equal to $Σ_0^{\rm th}=0.01955 c…
We propose a new class of cosmological unified dark sector models called "{\em Generalized Logotropic Models}". They depend on a free parameter $n$. The original logotropic model [P.H. Chavanis, Eur. Phys. J. Plus {\bf 130}, 130 (2015)] is a special case of our generalized model corresponding to $n=1$. In our scenario, the Universe is filled with a single fluid, a generalized logotropic dark fluid (GLDF), whose pressure $P$ includes higher order logarithmic terms of the rest-mass density $ρ_m$. The total energy density $ε$ is the sum of the rest-mass energy density $ρ_m c^2$ and the internal e…
Primordial Physics in the Nonlinear Universe: Revealing the oscillating halo bias from cosmological collider models
University of Chicago（芝加哥大学）；Kavli Institute for Cosmological Physics, University of Chicago（宇宙学物理卡弗里研究所，芝加哥大学）；Perimeter Institute for Theoretical Physics（理论物理 perimeter 研究所）
We investigate impacts of long-wavelength gravitational waves (GWs) on nonlinear structure formation by utilizing the tidal separate universe simulations. Based on the equivalence of a long-wavelength GW to a uniform tidal field in a local frame, we provide a way to incorporate a long-wavelength GW into the tidal separate universe simulation as an effective anisotropic expansion. This methodology enables us to study effects of GWs on large-scale structure efficiently. We measure the anisotropic imprint in the local power spectrum from the tidal separate universe simulations with GWs, which cor…
We use the Separate Universe technique to calibrate the dependence of linear and quadratic halo bias $b_1$ and $b_2$ on the local cosmic web environment of dark matter haloes. We do this by measuring the response of halo abundances at fixed mass and cosmic web tidal anisotropy $α$ to an infinite wavelength initial perturbation. We augment our measurements with an analytical framework developed in earlier work which exploits the near-Lognormal shape of the distribution of $α$ and results in very high precision calibrations. We present convenient fitting functions for the dependence of $b_1$ and…
We construct an emulator for the halo mass function over group and cluster mass scales for a range of cosmologies, including the effects of dynamical dark energy and massive neutrinos. The emulator is based on the recently completed Mira-Titan Universe suite of cosmological $N$-body simulations. The main set of simulations spans 111 cosmological models with 2.1 Gpc boxes. We extract halo catalogs in the redshift range $z=[0.0, 2.0]$ and for masses $M_{200\mathrm{c}}\geq 10^{13}M_\odot/h$. The emulator covers an 8-dimensional hypercube spanned by {$Ω_\mathrm{m}h^2$, $Ω_\mathrm{b}h^2$, $Ω_νh^2$,…
Within the Halo Model of large scale structure, all matter is contained in dark matter halos. This simple yet powerful framework has been broadly applied to multiple data sets and enriched our comprehension of how matter is distributed in the Universe. In this work we extend this assumption by allowing for matter to rest not only inside halos but also within cosmic voids and in between halos and voids (which we call 'dust'). This assumption leads to additional contributions (1Void, 2Void, Halo-Void, etc.) to the predictions of correlation functions, spectra and profiles for both halos and void…
ELUCID -- Exploring the Local Universe with the reConstructed Initial Density field. II: Reconstruction diagnostics, applied to numerical halo catalogs
Both simulation and observational data have shown that the spin and shape of dark matter halos are correlated with their nearby large-scale environment. As structure formation on different scales is strongly coupled, it is trick to disentangle the formation of halo with the large-scale environment, making it difficult to infer which is the driving force for the correlation between halo spin/shape with the large-scale structure. In this paper, we use N-body simulation to produce twin Universes that share the same initial conditions on small scales but different on large scales. This is achieved…
Cosmological $N$-body simulations of the dark matter component of the universe typically use initial conditions with a fixed power spectrum and random phases of the density field, leading to structure consistent with the local distribution of galaxies only in a statistical sense. It is, however, possible to infer the initial phases which lead to the configuration of galaxies and clusters that we see around us. We analyse the CSiBORG suite of 101 simulations, formed by constraining the density field within 155 Mpc$/h$ with dark matter particle mass $4.38\times10^9 M_\odot$, to quantify the degr…
As cosmic structures form, matter density fluctuations collapse gravitationally and baryonic matter is shock-heated and thermalized. We therefore expect a connection between the mean gravitational potential energy density of collapsed halos, $Ω_{W}^{\rm halo}$, and the mean thermal energy density of baryons, $Ω_{\rm th}$. These quantities can be obtained using two fundamentally different estimates: we compute $Ω_{W}^{\rm halo}$ using the theoretical framework of the halo model which is driven by dark matter statistics, and measure $Ω_{\rm th}$ using the Sunyaev-Zeldovich (SZ) effect which prob…
The thermal Sunyaev-Zeldovich effect contains information about the thermal history of the universe, observable in maps of the Compton $y$ parameter; however, it does not contain information about the redshift of the sources. Recent papers have utilized a tomographic approach, cross-correlating the Compton $y$ map with the locations of galaxies with known redshift, in order to deproject the signal along the line of sight. In this paper, we test the validity and accuracy of this tomographic approach to probe the thermal history of the universe. We use the state-of-the-art cosmological hydrodyna…
Massive, red galaxies in a hierarchical universe-II Clustering of Extremely Red Objects
利用半解析星系形成模型结合宇宙学N体模拟，对Λ冷暗物质宇宙中极红天体（ERO）的成簇进行了预测. ERO是在0.7< z < 3观测到的红色大质量星系，它们的数量和性质对分层星系形成模型提出了挑战。分析了ERO的晕占据分布和两点关联函数，探讨了这些量随视星等、色切和红移的变化规律。我们的模型预测的晕占据分布是显着不同的，通常假设。这是由于活动星系核反馈的加入，它改变了活动星系核反馈第一次变得重要的质量之上的亮度-宿主晕质量关系的斜率和散射。我们预测，平均而言，质量大于10^{13}h^{-1}Msun的暗物质晕至少有一个在1.5 < z < 2.5处的ERO。考虑到观测估计中的样本方差，对于（R-K）>5或（i-K）>4.5的ERO，预测的角聚类与当前观测结果相当一致。
X-ray feedback in the pre-reionization Universe provided one of the major energy sources for reionization and the thermal evolution of the early intergalactic medium. However, X-ray sources at high redshift have remained largely inaccessible to observations. One alternative approach to study the overall effect of X-ray feedback in the early Universe is a full cosmological simulation. Toward this goal, in this paper we create an analytic model of X-ray feedback from accretion onto supermassive black holes (SMBHs), to be used as a sub-grid model in future cosmological simulations. Our analytic m…
We use the technique of total satellite luminosity, L_sat, to probe the dark matter halos around active galactic nuclei in the SDSS Main Galaxy Sample. Our results focus on galaxies and AGN that are the central galaxy of their halo. Our two AGN samples are constructed from optical emission-line diagnostics and from WISE infrared colors. Both optically-selected and WISE-selected AGN have L_sat values twice as high as non-active galaxy samples when controlling for stellar mass and mean stellar age. This implies that the halos are twice as massive, but we cannot rule out that the increase in L_sa…
Structure Formation under Inelastic Two-Component Dark Matter: Halo Statistics and Matter Power Spectra in the High-$z$ Universe
University of Kansas（堪萨斯大学）；Troy University（特洛伊大学）；University of Florida（佛罗里达大学）；Flatiron Institute（平顿研究所）；University of Pennsylvania（宾夕法尼亚大学）；Princeton University（普林斯顿大学）；Massachusetts Institute of Technology（麻省理工学院）；University of Virginia（弗吉尼亚大学）
The Galaxy--Halo Connection in High-Redshift Universe: Details and Evolution of Stellar-to-Halo Mass Ratios of Lyman Break Galaxies on CFHTLS Deep Fields
We measure the Voronoi density probability distribution function (PDF) for both dark matter and halos in N-body simulations. For the dark matter, Voronoi densities represent the matter density field smoothed on a uniform mass scale, which approximates the Lagrangian density field. For halos, the Voronoi densities contain information about the local environment of each halo. We measure the halo virial masses, the total amount of dark matter within each halo Voronoi cell, and the halo Voronoi cell volumes, and we show how halo abundances depend on these three quantities. We then study the positi…
