The Study Of Observational Constraints On Dark Energy Models

In 1998 the type la supernovae (SNIa) investigations indicate that the expansion of present universe is speeding up rather than slowing down, which has been confirmed by the following cosmic explorations such as the cosmic microwave background (CMB), the clusters of galaxies, etc. In theory, this make people have to doubt the validity of standard cosmolog-ical model, though the standard cosmology got the great success in the past. Considering the evolution of the universe complies with four-dimensional standard cosmology, the accelerated expansion of the present universe is usually attributed to the fact that dark energy (DE) is an exotic component with negative pressure. In addition, the modified gravity theories (f(R)) and higher-dimensional theories are also studied to interpret the accelerating universe.In this thesis, on the basis of the current observed data several dark energy models are constrained. The thesis is divided into five chapters. Specifically, the former two chapters are the background knowledge including theory and experiment:standard cosmology and its problems (chapter 1), and the methodology of constraints on dark energy models using the observed data (chapter 2). The latter three chapters are our work. Firstly, three models as the unification of dark matter and dark energy such as Generalized Chaplygin Gas (GCG), Variable Chaplygin Gas (VCG) and Variable Generalized Chaplygin Gas (VGCG) model are constrained. Concretely, using the current observed data these CG model parameters are con-strained and the evolution of several cosmological quantities are discussed. In addition, three Chaplygin Gas (CG) models are discriminated by using the geometrical diagnostic method (chapter 3). Secondly, to remove the dependence of special properties of dark energy, one can expand the equation of state of dark energy, deceleration parameter, or other quanti-ties. This scenario is usually called the model independent method, which include kinematics and dynamics. By constraining the model independent method, the values of the transition redshift, current deceleration parameter and equation of state are obtained. Also, using the objective model selection criteria, including the Akaike information criterion (AIC) and the Bayesian information criterion (BIC), the strength of three dark energy models is estimated in this part (chapter 4). At last, for using the theory beyond the standard cosmology to interpret the accelerating universe, the observational constraints on five-dimensional bounce cosmological model are investigated, and it is shown tha.t this scenario well interpret the ac-celerating universe (chapter 5). In addition, the holographic dark energy model with varying gravitational constant is also discussed in this part.