现代宇宙学

• kalium

  2020-08-07
  Until now, we have focused solely on the two-point function: the angular correlation function, the velocity covariance, and the power spectrum. You might have wondered why little has been said about one-point functions, the number density of galaxies for example. To answer this question, first consider an extreme example. How many people are there in the universe? This clearly is an impossible question to answer with the tools we have developed. Putting aside the thorny question of the definition of a "person," we still would have to develop theories of star formation out of the gas in galaxies, then planet formation around stars, then the evolution of life via various biological processes. A prediction of the "person density" in the universe is beyond the scope of ... this book, t...
• kalium

  2020-06-19
  So we will drop any pretensions of connecting the generic scalar field which drives inflation to known physics. Making this connection is left as a homework problem for a future Nobel laureate.
• nëdm

  2021-07-19
  确认大尺度结构和CMB作为两个最大有可为的研究领域，只解决了一方面的问题。另一个非常重要的挑战是理解如何刻画这些结构分布的特征，使得理论能够与试验比较。简单地看图和定量检验宇宙学模型完全是两回事。为了实施这种检验，通常有用的方法是对问题中的结构分布进行里叶变换；我们将会看到，在傅里叶空间可以很容易地从小尺度分布中分离出大尺度信息。最引人注意的是，暴胀理论对宇宙的初始条件做出了具体的预言，今天这些预言已经有了观测结果。对于我而言，宇宙学最令人激动的、意义深远的发现是CMB各向异性的观测，它符合暴胀理论预言的特征形式