论文标题
几乎是FLRW宇宙，作为宏观重力的平均几何形状
An Almost-FLRW Universe as the Averaged Geometry in Macroscopic Gravity
论文作者
论文摘要
众所周知，时空平均是一个与构建爱因斯坦张量的通勤的操作。在宏观重力（MG）的框架中，协变平均过程，这种非交换性给出了平均场方程，并具有额外的校正项称为后反应。重要的是要探索这样的术语（即使已知很小）是否可能对精确宇宙学引起任何系统效应。在这项工作中，我们探讨了MG形式主义在几乎是Friedmann-Lema-Robertson-Walker（FLRW）模型中的应用。也就是说，我们发现使用线性扰动的FLRW公制的平均宇宙将平均宇宙几乎模拟的磁场方程的解决方案。我们研究了几种具有不同功能形式的度量扰动的溶液，包括平面波ansatzes。我们发现，反反应术语不仅存在于背景级别，而且在扰动级别上存在，这反映了平均过程的非线性性质。因此，平均效应可以扩展到宇宙中结构的膨胀和增长。
It is well-known that spacetime averaging is an operation that does not commute with building the Einstein tensor. In the framework of Macroscopic gravity (MG), a covariant averaging procedure, this non-commutativity gives averaged field equations with an additional correction term known as back-reaction. It is important to explore whether such a term, even if known to be small, may or may not cause any systematic effect for precision cosmology. In this work, we explore the application of the MG formalism to an almost Friedmann-Lemaître-Robertson-Walker (FLRW) model. Namely, we find solutions to the field equations of MG taking the averaged universe to be almost-FLRW modelled using a linearly perturbed FLRW metric. We study several solutions with different functional forms of the metric perturbations including plane waves ansatzes. We find that back-reaction terms are present not only at the background level but also at perturbed level, reflecting the non-linear nature of the averaging process. Thus, the averaging effect can extend to both the expansion and the growth of structure in the universe.
