What is the distance to the CMB?
What is the distance to the CMB?
复制标题
到中巴的距离是多少？
DOI：
10.1088/1475-7516/2014/11/036
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发表时间：
2014
影响因子：
6.4
通讯作者：
R. Durrer
中科院分区：
文献类型：
--
作者：
C. Clarkson;Obinna Umeh;R. Maartens;R. Durrer
精密宇宙学的成功不仅取决于准确的观测，还取决于理论模型——必须至少以相同的精度水平来理解理论模型。如果忽略微妙的相对论效应，可能会导致测量结果出现偏差。由于总光子通量的非线性相对论守恒，这样的效应之一使距离-红移关系远离其背景值而发生系统性偏移。我们还直接展示了这种转变是如何从测地偏差方程的完全相对论分析中得出的。我们使用关于一致性背景的二阶扰动推导了偏移的期望值，并表明到最后一次散射的距离增加了 1%。我们认为，忽略这种转变可能会导致背景宇宙学参数出现显着偏差，因为它改变了背景模型的含义。如果这种偏移确实是对背景的校正，则对 CMB 参数估计进行天真的调整会将从 CMB 推断的 H0 值提高 5%，从而可能消除 H0 局部测量的张力。当与本地 H0 数据结合时，其他依赖于距离的 CMB 参数也会偏移 ∼ 1σ。虽然我们的估计依赖于简单化的分析，但它们仍然表明，当我们的目标是确定亚百分比水平的模型参数时，根据可观测值的期望值准确定义背景模型至关重要。
The success of precision cosmology depends not only on accurate observations, but also on the theoretical model --- which must be understood to at least the same level of precision. Subtle relativistic effects can lead to biased measurements if they are neglected. One such effect gives a systematic shift in the distance-redshift relation away from its background value, due to the non-linear relativistic conservation of total photon flux. We also show directly how this shift follows from a fully relativistic analysis of the geodesic deviation equation. We derive the expectation value of the shift using second-order perturbations about a concordance background, and show that the distance to last scattering is increased by 1%. We argue that neglecting this shift could lead to a significant bias in the background cosmological parameters, because it alters the meaning of the background model. A naive adjustment of CMB parameter estimation if this shift is really a correction to the background would raise the H0 value inferred from the CMB by 5%, potentially removing the tension with local measurements of H0. Other CMB parameters which depend on the distance would also be shifted by ∼ 1σ when combined with local H0 data. While our estimations rely on a simplistic analysis, they nevertheless illustrate that accurately defining the background model in terms of the expectation values of observables is critical when we aim to determine the model parameters at the sub-percent level.
影响因子：
8.6
作者：
V. Marra;L. Amendola;I. Sawicki;W. Valkenburg
通讯作者：
V. Marra;L. Amendola;I. Sawicki;W. Valkenburg