On problems with cosmography in cosmic dark ages
On problems with cosmography in cosmic dark ages
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论宇宙黑暗时代的宇宙学问题
DOI：
10.1016/j.physletb.2021.136366
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发表时间：
2021
影响因子：
4.4
通讯作者：
M. M. Sheikh-Jabbari and T. Yang
中科院分区：
文献类型：
--
作者：
Aritra Banerjee;Eoin Colgain;Misao Sasaki;M. M. Sheikh-Jabbari and T. Yang
类星体作为 Ia 型超新星之外的高红移窗口中的标准烛光，显示出相当大的前景。最近，Risaliti、Lusso 和合作者 [1]、[2]、[3] 成功地生成了高红移哈勃图 (z≲ 7)，该图支持“类星体哈勃图可以通过标准平面 ΛCDM 模型很好地再现到 z∼ 1.5− 2 的趋势，但在较高红移时会出现强烈偏差”。这个结论取决于光度距离的对数多项式展开。在这篇文章中，我们证明了这种扩展（或其“改进”）通常只能在 z∼ 1.5− 2 范围内可信。因此，扩展有效性的崩溃可能会被误解为与平面 ΛCDM 的（虚拟）偏差。我们通过模拟数据示例进一步说明问题。
Quasars show considerable promise as standard candles in a high-redshift window beyond Type Ia supernovae. Recently, Risaliti, Lusso & collaborators [1],[2],[3] have succeeded in producing a high redshift Hubble diagram (z≲ 7) that supports “a trend whereby the Hubble diagram of quasars is well reproduced by the standard flat ΛCDM model up to z∼ 1.5− 2, but strong deviations emerge at higher redshifts”. This conclusion hinges upon a log polynomial expansion for the luminosity distance. In this note, we demonstrate that this expansion (or “improvements” thereof) typically can only be trusted up to z∼ 1.5− 2. As a result, a breakdown in the validity of the expansion may be misinterpreted as a (phantom) deviation from flat ΛCDM. We further illustrate the problem through mock data examples.