标题： 非标准重组能否解决哈勃张力？ 显示英文标题

标题： Can Non-standard Recombination Resolve the Hubble Tension?

摘要： 从宇宙微波背景（CMB）观测和本地距离阶梯测量中得出的不一致的哈勃常数值可能暗示了标准$\Lambda$CDM 模型之外的新物理。 在早期的研究中发现，至少从现象学的角度来看，非标准的再结合历史可以将$\gtrsim 4\sigma$哈勃张力减少到$\sim 2\sigma$。 沿着这条路径，我们在 RECFAST 中改变物理和现象学参数，该代码是计算宇宙电离历史的标准代码，以探索标准再结合之外的可能物理。 我们发现，CMB 对哈勃常数的约束对氢离子化能和$2s \rightarrow 1s$两个光子衰变率敏感，这两者都是原子常数，并且对再结合的其他细节不敏感。 因此，哈勃张力对再结合历史的扰动非常稳健，除非异常物理在再结合时期修改了原子常数。 显示英文摘要

摘要： The inconsistent Hubble constant values derived from cosmic microwave background (CMB) observations and from local distance-ladder measurements may suggest new physics beyond the standard $\Lambda$CDM paradigm. It has been found in earlier works that, at least phenomenologically, non-standard recombination histories can reduce the $\gtrsim 4\sigma$ Hubble tension to $\sim 2\sigma$. Following this path, we vary physical and phenomenological parameters in RECFAST, the standard code to compute ionization history of the universe, to explore possible physics beyond standard recombination. We find that the CMB constraint on the Hubble constant is sensitive to the Hydrogen ionization energy and $2s \rightarrow 1s$ two-photon decay rate, both of which are atomic constants, and is insensitive to other details of recombination. Thus, the Hubble tension is very robust against perturbations of recombination history, unless exotic physics modifies the atomic constants during the recombination epoch.