We explore the phenomenology of a two-fluid cosmological model, where the field equations of general relativity are sourced by baryonic and cold dark matter. We find that the model allows for a unified description of small and large scale, late-time cosmological dynamics. Specifically, in the static regime we recover the flattening of galactic rotation curves by requiring the matter density profile to scale as 1/r ². The same behavior describes matter inhomogeneities distribution at small cosmological scales. This traces galactic dynamics back to structure formation. At large cosmological scales, we focus on back reaction effects of the spacetime geometry to the presence of matter inhomogeneities. We find that a cosmological constant (CC) with the observed order of magnitude, emerges by averaging the back reaction term on spatial scales of order 100 Mpc and it is related in a natural way to matter distribution. This provides a resolution to both the CC and the coincidence problems and shows the existence of an intriguing link between the small and large scale behavior in cosmology.

我们探索双流体宇宙学模型的现象学，其中广义相对论的场方程源自重子和冷暗物质。我们发现该模型允许对小尺度和大尺度后期宇宙动力学进行统一描述。具体来说，在静态状态下，我们通过要求物质密度剖面按比例缩放为 1/ r ²来恢复星系旋转曲线的平坦化. 同样的行为描述了小宇宙尺度上的物质不均匀性分布。这将星系动力学追溯到结构形成。在大的宇宙学尺度上，我们关注时空几何对物质不均匀性的反作用效应。我们发现，通过对 100 Mpc 数量级的空间尺度上的逆反应项进行平均，可以得出一个具有观测数量级的宇宙学常数 (CC)，并且它以自然的方式与物质分布相关。这为 CC 和巧合问题提供了解决方案，并显示了宇宙学中小尺度和大尺度行为之间存在有趣的联系。