▪The Hubble parameter, H 0, is not an univocally defined quantity: It relates redshifts to distances in the near Universe, but it is also a key parameter of the ΛCDM standard cosmological model. As such, H 0 affects several physical processes at different cosmic epochs and multiple observables. We have counted more than a dozen H 0s that are expected to agree if (a) there are no significant systematics in the data and their interpretation and (b) the adopted cosmological model is correct.▪With few exceptions (proverbially confirming the rule), these determinations do not agree at high statistical significance; their values cluster around two camps: the low (68 km s1 Mpc1) and high (73 km s1 Mpc1) camps. It appears to be a matter of anchors. The shape of the Universe expansion history agrees with the model; it is the normalizations that disagree.▪Beyond systematics in the data/analysis, if the model is incorrect, there are only two viable ways to “fix” it: by changing the early time (z ≳ 1,100) physics and, thus, the early time normalization or by a global modification, possibly touching the model's fundamental assumptions (e.g., homogeneity, isotropy, gravity). None of these three options has the consensus of the community.▪The research community has been actively looking for deviations from ΛCDM for two decades; the one we might have found makes us wish we could put the genie back in the bottle.

中文翻译：

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许多 H0 的故事


▪哈勃参数 H 0 不是一个明确定义的量：它将红移与近宇宙中的距离联系起来，但它也是 ΛCDM 标准宇宙学模型的一个关键参数。因此，H 0 影响不同宇宙纪元和多个可观察对象的多个物理过程。我们已经数了十几个 H 0，如果 （a） 数据中没有重要的系统学及其解释，并且 （b） 所采用的宇宙学模型是正确的，那么这些决定在高统计显著性下不一致; ▪它们的值集中在两个阵营周围：低（68 km s1 Mpc1）和高（73 km s1 Mpc1）阵营。这似乎是一个锚的问题。宇宙膨胀历史的形状与模型一致;▪除了数据/分析中的系统学之外，如果模型不正确，只有两种可行的方法可以“修复”它：通过改变早期时间 （z ≳ 1,100） 物理学，从而改变早期时间归一化，或者通过全局修改，可能触及模型的基本假设（例如，均匀性、各向同性、重力）。这三个选项都没有得到社区的共识。▪二十年来，研究界一直在积极寻找与 ΛCDM 的偏差;我们可能找到的那个让我们希望能把精灵放回瓶子里。