arXiv 1806.025152018-06-07astro-ph.CO

存在系统误差的通货膨胀谱游程探索

The Quest for the Inflationary Spectral Runnings in the Presence of Systematic Errors

Xiaolei Li, Noah Weaverdyck, Saroj Adhikari, Dragan Huterer, Jessica Muir, Hao-Yi Wu

备注：: 15 pages, 9 figures, ApJ, in press
DOI：: 10.3847/1538-4357/aacaf7

摘要：

宇宙暴胀预言标量谱指数随尺度“运行”。因此，对频谱运行值$α_s\equiv \textrm{d} n_s/\textrm{d}\ln k$和$β_s\equiv \textrm{d}α_s/\textrm{d}\ln k$的限制提供了对暴胀物理学的基本检验。在这里，我们研究的可行性测量运行时，即将到来的大容量星系调查的信息被用来补充CMB-S4实验提供的信息，特别是专注于包括高- $k$，非线性尺度的影响。由于这些测量将是敏感的非线性功率谱的建模不确定性，我们研究如何三种不同的方式参数化这些系统-引入零，两个或几百个讨厌的参数-影响约束和保护参数偏差。仅考虑统计误差，我们发现，包括强非线性尺度可以大大收紧约束。然而，当我们将我们的分析限制在估计不受系统偏差强烈影响的尺度上时，这些约束减弱到比CMB-S4实验好不了多少的水平。考虑到这些因素，近期大尺度结构调查不太可能为第一次运行的$α_s$的CMB-S4测量增加太多信息。第二次运行$β_s$有更大的改进潜力，相对于单独使用CMB，大尺度结构信息将允许约束改进3- 4倍。虽然这些约束仍然高于慢卷暴胀的预测值，但它们确实探测了与非标准暴胀模型相关的参数空间区域，例如那些可以产生大量原始黑洞的模型。

英文摘要：

Cosmological inflation predicts that the scalar spectral index "runs" with scale. Constraints on the values of the spectral runnings, $α_s\equiv \textrm{d} n_s/\textrm{d}\ln k$ and $β_s\equiv \textrm{d}α_s/\textrm{d}\ln k$, therefore provide a fundamental test of the physics of inflation. Here we study the feasibility of measuring the runnings when information from upcoming large-volume galaxy surveys is used to supplement the information provided by a CMB-S4 experiment, particularly focusing on the effect of including high-$k$, nonlinear scales. Since these measurements will be sensitive to modeling uncertainties for the nonlinear power spectrum, we examine how three different ways of parameterizing those systematics---introducing zero, two, or several hundred nuisance parameters---affect constraints and protect against parameter biases. Considering statistical errors alone, we find that including strongly nonlinear scales can substantially tighten constraints. However, these constraints weaken to levels not much better than those from a CMB-S4 experiment alone when we limit our analysis to scales where estimates are not strongly affected by systematic biases. Given these considerations, near-future large-scale structure surveys are unlikely to add much information to the CMB-S4 measurement of the first running $α_s$. There is more potential for improvement for the second running, $β_s$, for which large-scale structure information will allow constraints to be improved by a factor of 3--4 relative to using the CMB alone. Though these constraints are still above the value predicted by slow roll inflation, they do probe regions of parameter space relevant to nonstandard inflationary models with large runnings, for example those that can generate an appreciable abundance of primordial black holes.

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