标题： 宏观引力平均宇宙中结构可观测量的扩展与增长 显示英文标题

标题： Expansion and Growth of Structure Observables in a Macroscopic Gravity Averaged Universe

摘要： 我们使用宏观引力（MG）的精确和协变框架，研究平均化非均匀性对膨胀和大尺度结构增长观测量的影响。众所周知，应用爱因斯坦方程和空间平均不交换，导致平均化问题。对于应用于弗里德曼-勒梅特-罗伯逊-沃尔克（FLRW）度规的MG形式，这给出一个额外的动力学项，表示为平均密度参数$\Omega_A$。平坦FLRW度规的MG精确各向同性宇宙学解在文献中已知，我们在这里推导出一个各向异性精确解。利用各向同性解，我们将膨胀历史与超新星距离、重子声学振荡、CMB最后散射面和哈勃常数测量的当前数据进行比较，发现$-0.05 \le \Omega_A \le 0.07$（在95%置信水平下）。对于平坦度规情况，这简化为$-0.03 \le \Omega_A \le 0.05$。我们还发现，将此项包含在拟合中可以将通常宇宙学参数的值改变几个到几个百分点。接下来，我们推导出MG中大尺度结构增长速率的方程，其中包括由于平均化而产生的项，并将其与LCDM一致模型的增长率进行比较。我们发现，幅度范围在上述限制内的$\Omega_A$导致晚期增长相对于LCDM的相对偏差高达2-4%。因此，增长的偏移可能与暗能量密度参数或其状态方程类似变化引起的偏移幅度相当。这种影响也可能与未来调查考虑的一些系统效应幅度相当。这表明，在未来的精密宇宙学研究中需要严格约束平均化项及其可能的影响。（摘要） 显示英文摘要

摘要： We investigate the effect of averaging inhomogeneities on expansion and large-scale structure growth observables using the exact and covariant framework of Macroscopic Gravity (MG). It is well-known that applying the Einstein's equations and spatial averaging do not commute and lead to the averaging problem. For the MG formalism applied to the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, this gives an extra dynamical term encapsulated as an averaging density parameter denoted $\Omega_A$. An exact isotropic cosmological solution of MG for the flat FLRW metric is already known in the literature, we derive here an anisotropic exact solution. Using the isotropic solution, we compare the expansion history to current data of distances to supernovae, Baryon Acoustic Oscillations, CMB last scattering surface, and Hubble constant measurements, and find $-0.05 \le \Omega_A \le 0.07$ (at the 95% CL). For the flat metric case this reduces to $-0.03 \le \Omega_A \le 0.05$. We also find that the inclusion of this term in the fits can shift the values of the usual cosmological parameters by a few to several percents. Next, we derive an equation for the growth rate of large scale structure in MG that includes a term due to the averaging and compare it to that of the LCDM concordance model. We find that an $\Omega_A$ of an amplitude range within the bounds above leads to a relative deviation of the growth from that of the LCDM of up to 2-4% at late times. Thus, the shift in the growth could be of comparable amplitude to that caused by similar changes in cosmological parameters like the dark energy density parameter or its equation of state. The effect could also be comparable in amplitude to some systematic effects considered for future surveys. This indicates that the averaging term and its possible effect need to be tightly constrained in future precision cosmological studies. (Abridged)