arXiv 2107.124652021-07-26astro-ph.CO

变化的基本常数主成分分析：关于哈勃张力的附加提示

Varying fundamental constants principal component analysis: additional hints about the Hubble tension

Luke Hart, Jens Chluba

备注：: 22 pages, 25 figures, submitted to MNRAS
DOI：: 10.1093/mnras/stab2777

摘要：

变化的基本常数（VFC）[例如，精细结构常数$α_{\rm EM}$]可以在许多扩展宇宙学中出现。通过它们在最后散射和再电离过程中对重子和光子退耦的影响，这些模型可以直接使用宇宙微波背景（CMB）温度和偏振各向异性的测量来约束。以前的研究主要集中在与时间无关的基本常数的值的变化。在这里，我们推广到时间依赖的变化。而不是直接研究各种VFC参数化，我们进行独立于模型的主成分分析（PCA），直接使用重组过程中的变化常数的本征模分解。在发展了形式主义之后，我们使用普朗克2018年的数据来获得新的VFC极限，表明目前可以约束三个独立的VFC模式。没有迹象表明显着偏离标准模型与普朗克数据。宇宙方差有限的模式进行了比较，并进行了简单的预测西蒙斯天文台，表明在未来的改进目前的约束的一个因素的$\simeq 3$可以预期。我们的模式只集中在VFC在红移$z\geq 300$。这意味着它们没有捕捉到与再电离时代有关的一些自由度。这方面提供了重要的新的见解，可能的起源哈勃紧张，暗示确实是一个联合修改的重组和再电离物理可能在工作。正如我们在这里强调的，同时涵盖复合和再电离的扩展PCA可以更好地解释这个问题。

英文摘要：

Varying fundamental constants (VFC) [e.g., the fine-structure constant, $α_{\rm EM}$] can arise in numerous extended cosmologies. Through their effect on the decoupling of baryons and photons during last scattering and reionisation, these models can be directly constrained using measurements of the cosmic microwave background (CMB) temperature and polarization anisotropies. Previous investigations focused mainly on time-independent changes to the values of fundamental constants. Here we generalize to time-dependent variations. Instead of directly studying various VFC parameterizations, we perform a model-independent principal component analysis (PCA), directly using an eigenmode decomposition of the varying constant during recombination. After developing the formalism, we use Planck 2018 data to obtain new VFC limits, showing that three independent VFC modes can be constrained at present. No indications for significant departures from the standard model are found with Planck data. Cosmic variance limited modes are also compared and simple forecasts for The Simons Observatory are carried out, showing that in the future improvements of the current constraints by a factor of $\simeq 3$ can be anticipated. Our modes focus solely on VFC at redshifts $z\geq 300$. This implies that they do not capture some of the degrees of freedom relating to the reionisation era. This aspect provides important new insights into the possible origin of the Hubble tension, hinting that indeed a combined modification of recombination and reionisation physics could be at work. An extended PCA, covering both recombination and reionisation simultaneously, could shed more light on this question, as we emphasize here.

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