The observation of space-time variations in fundamental constants would provide strong evidence for the existence of new light degrees of freedom in the theory of Nature. Robustly constraining such scenarios requires exploiting observations that span different scales and probe the state of the Universe at different epochs. In the context of cosmology, both the cosmic microwave background and the Lyman-$\alpha$ forest have proven to be powerful tools capable of constraining variations in electromagnetism, however at the moment there do not exist cosmological probes capable of bridging the gap between recombination and reionization. In the near future, radio telescopes will attempt to measure the 21cm transition of neutral hydrogen during the epochs of reionization and the cosmic dawn (and potentially the tail end of the dark ages); being inherently sensitive to electromagnetic phenomena, these experiments will offer a unique perspective on space-time variations of the fine-structure constant and the electron mass. We show here that large variations in these fundamental constants would produce features on the 21cm power spectrum that may be distinguishable from astrophysical uncertainties. Furthermore, we forecast the sensitivity for the Square Kilometer Array, and show that the 21cm power spectrum may be able to constrain variations at the level of ${\cal O}(10^{-3})$.

中文翻译：

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宇宙黎明时基本常数的变化

对基本常数的时空变化的观察将为自然理论中新的光自由度的存在提供强有力的证据。强有力地限制这些情景需要利用跨越不同尺度的观测并探索不同时期的宇宙状态。在宇宙学的背景下，宇宙微波背景和 Lyman-$\alpha$ 森林都被证明是能够限制电磁变化的强大工具，但是目前还没有能够弥合重组之间差距的宇宙学探测器和再电离。在不久的将来，射电望远镜将尝试测量再电离时代和宇宙黎明（可能是黑暗时代的尾声）期间中性氢的 21 厘米跃迁；由于对电磁现象天生敏感，这些实验将为精细结构常数和电子质量的时空变化提供独特的视角。我们在这里表明，这些基本常数的巨大变化会在 21 厘米功率谱上产生特征，这些特征可能与天体物理不确定性区分开来。此外，我们预测了平方公里阵列的灵敏度，并表明 21 厘米功率谱可能能够将变化限制在 ${\cal O}(10^{-3})$ 水平。我们在这里表明，这些基本常数的巨大变化会在 21 厘米功率谱上产生特征，这些特征可能与天体物理不确定性区分开来。此外，我们预测了平方公里阵列的灵敏度，并表明 21 厘米功率谱可能能够将变化限制在 ${\cal O}(10^{-3})$ 水平。我们在这里表明，这些基本常数的巨大变化会在 21 厘米功率谱上产生特征，这些特征可能与天体物理不确定性区分开来。此外，我们预测了平方公里阵列的灵敏度，并表明 21 厘米功率谱可能能够将变化限制在 ${\cal O}(10^{-3})$ 水平。