Cosmodynamical issues in an accelerated universe

Zusammenfassung

This thesis studies the cosmodynamics of dark energy and as well this concept in the already resurrected Eddington's proposal for the gravitational action in the presence of a cosmological constant and extends it to include matter fields. The existence of the cosmodynamics idea led us, in first place, to investigate the tension between the real Type Ia SNe (SNeIa) and baryon acoustic oscillations (BAO), and also between synthetic samples of these in dark energy equation of state reconstructions such as the well known CPL model and a low correlation version. In particular, for this research, we explore the influence of priors on the tension issue. In the second place, the dynamics involved in a homogeneous and isotropic universe where the uncanny dark energy apparently drives the accelerated expansion led us to ask if the consideration of a new gravitational action can establish an alternative theory of the Big Bang and what will be its effects in a perturbed landscape. An answer to this question results in our proposal where the modifications to Einstein gravity are strong and the effects of the tensor perturbations are linearly unstable. Furthermore, the acceleration phase can be regarded as due to effects arising from the string landscape. In a previous work the influence of closed string tachyons was considered as the responsible of this acceleration/contraction, however, when a Chaplygin gas is incorporated the acceleration phase can be established under certain circumstances detailed in this work. Last, but not least, we headed to another subsector of the cosmology: Cosmography, which provides a model-independent way to map the expansion history of the universe. In this research we show that future BAO data have the potential to check this behaviour as well as to provide a way to discriminate between the LCDM model and alternative proposals of cosmic acceleration.