First year Wilkinson Microwave Anisotropy Probe results: Cosmological parameters and implications for inflation.

摘要

This thesis describes the analysis of the first year Wilkinson Microwave Anisotropy Probe (WMAP) data, and investigates its implications for cosmology and inflation. We begin by presenting our methodology for comparing the WMAP measurements of the cosmic microwave background (CMB) and other complementary data sets to theoretical models. We describe our use of the likelihood function, showing how the statistical and systematic uncertainties in the model and the data are propagated through the full analysis. Using the Monte Carlo Markov Chain (MCMC) technique, we explore the likelihood of the data given a model to determine the best fit cosmological parameters and their uncertainties. We find that the emerging standard model of cosmology, a flat &Lgr;-dominated universe seeded by a nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data alone. This simple model is also consistent with a host of other astronomical measurements obtained with a variety of different techniques, at different scales and redshifts. An unexpected result from this model, driven by WMAP's measurement of the temperature-polarization (TE) cross-power spectrum, is that the universe was reionized earlier than previously thought, ruling out warm dark matter. By combining WMAP data with other astronomical data, we constrain the geometry of the universe, the equation of state of the dark energy, and the energy density in stable neutrino species. Then, we confront the predictions of inflation, the currently dominant theory of structure formation, with the WMAP data, both alone and in combination with large scale structure data. Inflation is supported by the flatness of the universe, the Gaussianity and near-scale-invariance of primordial power spectra and the adiabatic superhorizon fluctuations at the time of decoupling implied by the TE data. Using constraints on the shape of the scalar power spectrum and the amplitude of gravity waves, we investigate the parameter space of inflationary models that is consistent with the data, putting upper limits on the tensor modes and correlated isocurvature modes. Finally, we investigate future prospects for cosmology using WMAP results after 4, 6 and 8 years of operation.