High Precision Cosmology with CMB Data

In this thesis we investigate the two cosmic epochs of inflation and recombination, through their imprints on the temperature and polarization anisotropies of the cosmic microwave background radiation. To probe the early universe we develop a map-based maximum-likelihood estimator to measure the amplitude of inflation-induced gravity waves, parametrized by $r$, from the cosmic microwave background (CMB) polarization maps. Being optimal by construction, the estimator avoids $E$-$B$ mixing, a possible source of contamination in the tiny $B$-mode detection, the target of many current and near future CMB experiments. For various observational cases, we probe the dependence of $r$ measurement on the signal from different scales of $E$ and $B$ polarization. We make forecasts for Spider-like and Planck-like experimental specifications and to investigate the sky-coverage optimization of the Spider-like case. We also use a novel information-based framework to compare how different generations of CMB experiments reveal information about the early universe, through their measurements of $r$. We also probe the epoch of recombination by investigating possible fluctuations in the free electron fraction $\Xe$ around the fiducial model of the standard recombination scenario. Though theoretically well studied, the detailed assumptions in the recombination history, based on standard atomic physics, have never been directly tested. However, for our CMB-based cosmological inferences to be reliable, the recombination scenario needs to be observationally verified. We approach this problem in a model-independent way and construct rank-ordered parameter eigen-modes with the highest power to probe $\Xe$. We develop an information-based criterion to truncate the eigen-mode hierarchy, which can be used in similar hierarchical model selections as well. The method is applied to simulations of Planck+ACTPol and a cosmic variance limited survey with differing simulated recombination histories and recovered $\Xe$ trajectories are constructed. We apply the method to currently available CMB datasets, WMAP9+ACT/SPT. The first constructed eigen-mode turns out to be a direct measure of the damping envelope. Its current measurement with SPT slightly indicates a damping tail anomaly, while ACT data agree well with the standard scenario. High resolution Planck data will resolve this tension with high significance.Ph