Sharpening Our Observational Tools to Nail Down the Nature of Dark Energy.

Abstract

This dissertation investigates systematic effects and performs new cosmological tests with observational probes of dark energy in anticipation of the precision dark energy constraints expected in the near future. Chapters 2-4 study systematic effects in dark energy probes, focusing on constraints from distance measurements, like those from Type Ia supernovae (SNe Ia). In Chapter 2, we quantify the effect of current SN Ia systematic errors on dark energy constraints, both for simple parametrizations of the equation of state and for a general description with principal components. Chapter 3 investigates recent evidence for a phantom equation of state using three separate SN Ia compilations, introducing new tests to search for systematic effects in the data. Chapter 4 is concerned with photometric calibration errors in the galaxy power spectrum. We highlight the danger of multiplicative errors and, using a Fisher matrix formalism, demonstrate a simple way to mitigate these errors. Chapters 5-6 focus on tests of the standard cosmological model. In Chapter 5, we use Bayesian model comparison techniques with model-independent SN Ia and BAO data to directly test power law expansion as an alternative cosmological model. In Chapter 6, we use low-redshift SN Ia data to test for the presence of the peculiar velocity correlations predicted by the standard model. We clarify how these are connected to the bulk velocity of local structure.