标题： 早期宇宙的约束 显示英文标题

标题： Early Cosmology Constrained

摘要： 我们通过探索在$\Lambda$CDM模型之外的不同组分可以放置多少额外的能量密度，来研究我们对早期宇宙宇宙学的了解。 为了做到这一点，我们使用一种方法来分离观测数据中包含的早期和晚期宇宙信息，从而显著减少结论对模型的依赖性。 我们发现，在再结合时期早期宇宙的额外能量成分的95%可信区域为：非加速的额外流体密度参数$\Omega_{\rm MR} < 0.006$以及以额外有效中微子种类形式参数化的额外辐射参数$2.3 < N_{\rm eff} < 3.2$，当施加平坦性条件时。 我们的约束表明，即使以这种很大程度上与模型无关的方式分析数据，当前观测结果也严重限制了在早期宇宙中隐藏超出$\Lambda$CDM的额外能量成分的可能性。 我们还发现，标准标尺——辐射拖拽时的声音视界，可以通过一种不依赖于晚期宇宙假设的方式很好地确定，但强烈依赖于早期物理过程，特别是像辐射一样行为的额外成分。 我们发现，以这种方式确定的标准标尺长度是$r_{\rm s} = 147.4 \pm 0.7$Mpc，如果辐射和中微子成分是标准的，但当允许非标准的暗辐射成分时，不确定性会增加一个数量级，达到$r_{\rm s} = 150 \pm 5$Mpc。 显示英文摘要

摘要： We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the $\Lambda$CDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95\% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter $\Omega_{\rm MR} < 0.006$ and extra radiation parameterised as extra effective neutrino species $2.3 < N_{\rm eff} < 3.2$ when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond $\Lambda$CDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is $r_{\rm s} = 147.4 \pm 0.7$ Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to $r_{\rm s} = 150 \pm 5$ Mpc.