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arXiv 2002.06988gr-qcastro-ph.COhep-th
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各向异性流体宇宙学：暗物质的替代方案？

Anisotropic Fluid Cosmology: an Alternative to Dark Matter?

Mariano Cadoni, Andrea P. Sanna, Matteo Tuveri

备注：
20 pages, 1 figure
发表信息：
Phys. Rev. D 102, 023514 (2020)
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摘要：

我们用各向异性流体宇宙学来描述目前暗能量占主导地位的宇宙。类似于已经提出的星系动力学，各向异性流体给出了重子物质，暗能量和它们可能的相互作用的有效描述，而不假设暗物质的存在。由此产生的各向异性流体时空自然会在小尺度上产生不均匀性，由各向异性应力触发，因此可能是这些尺度上结构形成的原因。通过求解宇宙学方程，我们证明了尺度因子$a$的动力学可以用通常的FLRW宇宙学来描述，并且完全不同于描述不均匀性的动力学。我们假设宇宙学各向异性流体继承了用于描述星系旋转曲线的状态方程。我们表明，在大尺度制度，流体可以被描述为一个广义的Chaubergin气体和适合的距离模量实验数据的Ia型超新星，从而正确地模拟所观察到的宇宙加速膨胀。相反，在小尺度区域，我们使用宇宙学扰动理论推导出质量密度分布的功率谱$P(k)$。在短波长下，我们发现一个$1/k^4$行为，在很好地符合所观察到的关联函数的物质分布在小尺度。

英文摘要：

We use anisotropic fluid cosmology to describe the present, dark energy-dominated, universe. Similarly to what has been proposed for galactic dynamics, the anisotropic fluid gives an effective description of baryonic matter, dark energy and their possible interaction, without assuming the presence of dark matter. The resulting anisotropic fluid spacetime naturally generates inhomogeneities at small scales, triggered by an anisotropic stress, and could therefore be responsible for structure formation at these scales. Solving the cosmological equations, we show that the dynamics of the scale factor $a$ is described by usual FLRW cosmology and decouples completely from that describing inhomogeneities. We assume that the cosmological anisotropic fluid inherits the equation of state from that used to describe galaxy rotation curves. We show that, in the large scale regime, the fluid can be described as a generalized Chaplygin gas and fits well the distance modulus experimental data of type Ia supernovae, thus correctly modelling the observed accelerated expansion of the universe. Conversely, in the small scale regime, we use cosmological perturbation theory to derive the power spectrum $P(k)$ for mass density distribution. At short wavelengths, we find a $1/k^4$ behaviour, in good accordance with the observed correlation function for matter distribution at small scales.

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