Beyond the Standard Model of Cosmology: Dark Energy, Massive Neutrinos, and Primordial Non-Gaussianity

I explore the ability of present and future data to constrain deviations in the standard model of cosmology, via observational signatures of dark energy, massive neutrinos, and primordial non-Gaussianity. To this end, I determine the extent to which our present constraints on the sum of neutrino masses and light degrees of freedom are affected by our ignorance of the curvature of the universe, running of the spectral index, primordial helium abundance, and alternative models of dark energy. I also explore the viability of massive sterile neutrinos in the universe. I forecast the expected constraints on dark energy and massive neutrinos from a combination of probes of the universal expansion rate and matter perturbation growth, in the form of weak lensing tomography, galaxy tomography, supernovae, and the cosmic microwave background, incorporating all relevant cross-correlations between the observables. I examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future lensing probes. In particular, I determine the precision with which dark energy modifications to the nonlinear matter power spectrum must be incorporated to avoid introducing significant bias in the lensing measurements. Moreover, I consider the impact of primordial non-Gaussianity on the ionization power spectrum from 21 cm emission during the epoch of reionization. I focus on the power spectrum on large scales at redshifts of 7 to 8 and explore the expected constraints on non-Gaussianity of the local form for current and next-generation 21 cm experiments.