Introduction

Abstract

The common assumption in modern cosmology is that the Universe is statistically homogeneous and isotropic, and therefore can be accurately described by the Friedmann-Robertson-Walker (FRW) metric which has one degree of freedom, the cosmic scale factor, \(a(t)\). In the current cosmological model, our Universe has evolved from a homogeneous state after the big bang to a highly inhomogeneous state of galaxies and clusters of galaxies, the energy density of which is composed of 4 % baryons, 22 % dark matter and 74 % dark energy today. The success of the ‘hot big bang’ model is clear from observations such as the microwave background blackbody radiation from the early Universe and from predictions of light element abundances from big bang nucleosynthesis. Despite this, there remain several challenges which the model fails to overcome, such as the nature of the inflationary mechanism and the presence of dark matter and dark energy. The growth of large scale structure in the Universe is an extremely important tool which can be used to probe fundamental physics such as the nature of dark energy and the theory of gravity. Structure formation is driven by a competition between the expansion of the Universe and gravitational attraction. By measuring the rate at which overdensities grow and their clustering statistics we can test different cosmological models. This chapter reviews the growth of density perturbations, the evidence for the accelerating cosmic expansion and discusses viable models which can solve the dark energy problem. We also present an overview of current and future probes of dark energy and modified gravity. In the coming years, new galaxy surveys and other cosmological observations will provide very precise measurements of the properties of dark energy. The work presented in this thesis uses state of the art modelling of dark energy cosmologies to provide accurate theoretical predictions for several cosmological probes.KeywordsDark MatterDark EnergyCosmic Microwave BackgroundDark Energy ModelWilkinson Microwave Anisotropy ProbeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.