In this paper, we investigate anisotropic fluid cosmology in a situation where the space–time metric back-reacts in a local, time-dependent way to the presence of inhomogeneities. We derive exact solutions to the Einstein field equations describing Friedmann–Lemaítre–Robertson–Walker (FLRW) large-scale cosmological evolution in the presence of local inhomogeneities and time-dependent backreaction. We use our derivation to tackle the cosmological constant problem. A cosmological constant emerges by averaging the backreaction term on spatial scales of the order of 100 Mpc, at which our universe begins to appear homogeneous and isotropic. We find that the order of magnitude of the “emerged” cosmological constant agrees with astrophysical observations and is related in a natural way to baryonic matter density. Thus, there is no coincidence problem in our framework.

中文翻译：

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各向异性流体宇宙学中宇宙学常数的出现

在本文中，我们研究了在时空度量以局部的、时间相关的方式对不均匀性的存在进行反向反应的情况下的各向异性流体宇宙学。我们推导出描述 Friedmann-Lemaítre-Robertson-Walker (FLRW) 大规模宇宙学演化的爱因斯坦场方程的精确解，其中存在局部不均匀性和时间相关的逆反应。我们使用我们的推导来解决宇宙常数问题。通过在 100 Mpc 量级的空间尺度上对反反应项进行平均，就会出现一个宇宙常数，此时我们的宇宙开始呈现均匀和各向同性。我们发现“出现”的宇宙学常数的数量级与天体物理学观察一致，并且以自然的方式与重子物质密度相关。因此，