Topics in Early Universe Cosmology

点击翻译按钮获取中文摘要

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.