Topics in Early Universe Cosmology

探索宇宙结构的新观测窗口正在打开。高精度的小角比尺微波各向异性图目前为我们提供了关于早期宇宙的令人兴奋的信息，而包含更多信息的微波极化图将很快可用。新的望远镜即将上线，它将绘制出高红移星系的分布，而观测宇宙学家正在计划对宇宙进行21厘米红移调查，这将确定重子物质的分布，甚至在恒星形成开始之前。我研究的一个中心主题是研究我们可以从这些关于基础物理的新调查中学到什么。早期宇宙的迅速膨胀提供了一种显微镜，可以延伸到可见的尺度——在非常早期的宇宙中，长度尺度对应的能量尺度要高得多，甚至比在最高能量的地球加速器上探索的能量尺度还要高得多。在一条研究路线中，我的团队将在上述新的观测窗口中寻找宇宙弦（量子场论中的拓扑缺陷，类似于晶体中的线缺陷）的特征。目前，宇宙学观测可以用早期宇宙的标准范式很好地解释，即所谓的暴胀“Lambda CDM”情景。对这个模型进行进一步的检查是很重要的。此外，这种情况虽然在现象上是成功的，但也存在一些概念上的问题。在第二条研究路线中，我们将考虑替代暴胀情景的方法，如弦气体宇宙论或“弹跳宇宙”范式。我们将尝试找到对这些情景的改进实现，并制定出新的预测，以便将它们与暴胀情景区分开来。我研究的第三个主题是暗能量，这是一种神秘的成分，目前占宇宙能量的三分之二以上。

New observational windows to probe the structure of our universe are opening up. High accuracy small angular scale microwave anisotropy maps are currently providing us with exciting information about the early universe, and microwave polarization maps which contain even more information will soon be available. New telescopes are coming online which will map out the distribution of galaxies at high redshifts, and observational cosmologists are working on plans for 21cm redshift surveys of the universe which will determine the distribution of baryonic matter even before the onset of star formation. A central theme of my research is to study what we can learn from these new surveys about fundamental physics. The rapid expansion of the early universe provides a microscope which stretches to visible scales length scales which in the very early universe correspond to energy scales much higher even than those explored at the highest energy terrestrial accelerators. In one line of research, my team will search for signatures of cosmic strings (topological defects in quantum field theories which are analogous to line defects in crystals) in the above-mentioned new observational windows. Currently, cosmological observations can be well explained by a standard paradigm of the early universe, namely the so-called inflationary "Lambda CDM" scenario. It is important to develop further checks of this model. Also, this scenario, although phenomenologically successful, suffers from a number of conceptual problems. In a second line of research we will consider alternatives to the inflationary scenario such as string gas cosmology or the "bouncing universe" paradigm. We will attempt to find improved realizations of these scenarios and work out new predictions with which they can be distinguished from the inflationary scenario. A third theme of my research will be on dark energy, the mysterious component which currently makes up more than two thirds of the energy of the universe.