25 pages, 6 figures, 1 table; (v2) constraints are reanalyzed using a tomography 21cm survey, conclusions unchanged, some references added, accepted for publication in JCAP
We discuss how one can discriminate models with cold dark matter (CDM) and baryon isocurvature fluctuations. Although current observations such as cosmic microwave background (CMB) can severely constrain the fraction of such isocurvature modes in the total density fluctuations, CMB cannot differentiate CDM and baryon modes by the shape of its power spectra. However, the evolution of CDM and baryon density fluctuations are different for each model, thus it would be possible to discriminate those isocurvature modes by extracting information on the fluctuations of CDM/baryon itself. We discuss that observations of 21 cm fluctuations can in principle differentiate these modes and demonstrate to what extent we can distinguish them with future 21 cm surveys. We show that, when the isocurvature mode has a large blue-tilted initial spectrum, 21 cm survey can clearly probe the difference.
Cold Dark Matter Isocurvature Perturbations: Constraints and Model Selection
我们利用CMB（WMAP和ACBAR）、大尺度结构（SDSS发光红星系）和超新星（SNLS）数据来限制CDM等曲率模对原始扰动谱的可能贡献。我们考虑三种不同的混合物绝热模式在一个平坦的$Λ$ CDM宇宙学没有张量模式：固定的相关性与一个单一的光谱指数;一般的相关性与一个单一的光谱指数;和一般的相关性与独立的光谱指数为每个模式。对于固定的相关性，我们验证了WMAP分析完全不相关和反相关的模式，而对于一般的相关性与一个单一的指标，我们发现一个小收紧的约束的分数贡献的isocurvature模式观察到的功率超过早期的工作。对于一般相关的模式和独立的光谱指数，我们的结果是完全不同的，以前的工作，需要加倍的先验空间的isocurvature光谱指数，以充分探索该地区的高可能性。标准的马尔可夫链蒙特卡罗技术被证明是不适合这个特定的应用程序，而不是我们的结果与嵌套采样。我们还使用贝叶斯证据，计算简单的嵌套采样算法，比较模型，发现纯绝热模型优于我们所有的isocurvature模型。这种倾向是这样的，贝叶斯因子的对数，$\mathrm{ln} B < -2$的所有模型和$\mathrm{ln} B < -5$的情况下，完全反相关的模式与一个单一的光谱指数（曲率的情况下）和一般相关的模式与一个单一的光谱指数。
Constraints on scalar and tensor perturbations in phenomenological and two-field inflation models: Bayesian evidences for primordial isocurvature and tensor modes
Primordial black hole clustering from spectator fields for interpreting the JWST observations
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台暗物质与空间天文重点实验室）；School of Astronomy and Space Science, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Department of Physics, College of Sciences, Northeastern University（东北大学理学院物理系）
