[论文解读] Spectral Distortions of the CMB as a Probe of Inflation, Recombination,
 Structure Formation and Particle Physics

Jens Chluba, A. Kogut+99 more|arXiv (Cornell University)|Jan 1, 2019

Cosmology and Gravitation Theories被引用 33

一句话总结

本文主张将CMB光谱失真作为对膨胀、再组合、再电离、结构形成以及超越标准模型粒子物理的强大、互补探针。

ABSTRACT

Following the pioneering observations with COBE in the early 1990s, studies
 of the cosmic microwave background (CMB) have focused on temperature and
 polarization anisotropies. CMB spectral distortions - tiny departures of the
 CMB energy spectrum from that of a perfect blackbody - provide a second,
 independent probe of fundamental physics, with a reach deep into the primordial
 Universe. The theoretical foundation of spectral distortions has seen major
 advances in recent years, which highlight the immense potential of this
 emerging field. Spectral distortions probe a fundamental property of the
 Universe - its thermal history - thereby providing additional insight into
 processes within the cosmological standard model (CSM) as well as new physics
 beyond. Spectral distortions are an important tool for understanding inflation
 and the nature of dark matter. They shed new light on the physics of
 recombination and reionization, both prominent stages in the evolution of our
 Universe, and furnish critical information on baryonic feedback processes, in
 addition to probing primordial correlation functions at scales inaccessible to
 other tracers. In principle the range of signals is vast: many orders of
 magnitude of discovery space could be explored by detailed observations of the
 CMB energy spectrum. Several CSM signals are predicted and provide clear
 experimental targets, some of which are already observable with present-day
 technology. Confirmation of these signals would extend the reach of the CSM by
 orders of magnitude in physical scale as the Universe evolves from the initial
 stages to its present form. The absence of these signals would pose a huge
 theoretical challenge, immediately pointing to new physics.

研究动机与目标

• 以光谱失真作为超越CMB各向异性的全新、丰富的可观测量的动机。
• 解释失真如何编码从早期到今天的热史。
• 突出与膨胀、暗物质、再组合和再电离的联系。
• 讨论实验前景及下一代光谱学可能带来的收益。

提出的方法

• 描述mu型、y型和r型失真的物理起源，来自能量释放和光子相互作用。
• 解释失真如何来自小尺度扰动的Silk阻尼以及来自再组合辐射。
• 概述关键失真信号（mu、y、CRR）的预计振幅及它们对宇宙学参数的依赖。
• 讨论实验概念（PIXIE、PRISM）以及在检测光谱失真时的前景污染挑战。
• 主张采用多探针、太空基的方式来获取完整的失真光谱。

实验结果

研究问题

• RQ1 CMB光谱失真能否在各向异性探针之外，测量小尺度的原始扰动（k ~ 1–10^4 Mpc^-1）？
• RQ2 mu、y、和r型失真能揭示关于膨胀、暗物质和再组合物理的哪些信息？
• RQ3 失真各向异性如何补充标准CMB测试，探测非高斯性和替代的早期宇宙情景？
• RQ4 为在预测水平检测到失真，需要哪些实验配置和前景清洁策略？
• RQ5 CRR及其他失真特征如何约束诸如氦丰度和中微子性质等宇宙学参数？

主要发现

• mu失真在接近尺度不变扰动下预测为大约 mu ≈ (2.3 ± 0.14) × 10^-8，为小尺度功率提供杠杆。
• 失真编码从大爆炸后数月到现在的过程信息，访问各向异性无法到达的尺度。
• 再电离和结构形成贡献可观的y失真（y ≈ 几×10^-6），并且有与气体温度相关的相对论修正。
• 宇宙学再组合辐射（CRR）产生丰富的氢、氦再组合的光谱结构，揭示再组合动力学和原始丰度。
• 非热过程和新物理情景（如奇异衰变、暗物质相互作用）留下独特的失真信号，可探测超越ΛCDM的物理。
• 光谱失真提供对标准模型和膨胀的互补检验，结合其他探针时可能约束或揭示新物理。