Dark Energy And Dark Matter And The Observed Effect Study

In this thesis, we study some issues concerning dark energy and dark matter and their obser-vational effects. The thesis contents include four topics.Firstly, the dissociation of a bound system in a phantom field model is studied in this thesis.Using the effective metric of a bound system in an expanding universe and two solvable phan-tom models, the expression when the system becomes unbound is derived, and the effect of theparameter of the model in different bound systems is discussed. Then we study the different pa-rameterizations of dark energy equation of state from the perspective of Fisher information matrix.We show, from the data inference point of view, which parameterization is favored.Secondly, the cosmological dynamics is investigated in the framework of TeVeS (tensor-vector-scalar). We find that there is a late-time de sitter attractor in the evolution of universe whichnaturally provides an alternative mechanism of the nowadays accelerating expansion. Moreover,we argue that the effective cosmological constant of order O(k) is obtained without fine-tuning.Next, we study the internal metric of stars in TeVeS theory. We show the Oppenheimer-Volkoffequation in TeVeS theory, and get the metric and pressure inside the stars to order of post-Newtonian corrections. Then we investigate the features of motion around the static, sphericallysymmetric stars by Hamilton-Jacobi mothod.Thirdly, we review the global k-monopoles with a non-canonical kinetic term. The prop-erties of global k-monopoles are different from the standard ones because of the existence ofnon-standard kinetic term. Then, we study the gravitating global k-monopoles. A gravitatingglobal k-monopole produces a tiny gravitational field outside the core in addition to a solid an-gular deficit in the k-field theory. As a new feature, the gravitational field can be attractive orrepulsive depending on the non-canonical kinetic term.Finally, we review the relationship between the scalar-tensor theory and f(R) theory withtwo formalism, which include metric formalism and Paltatini formalism. Then, using the elegantmethod employed recently by Erickcek, Smith and Kamionkowski, on the premise that the space-time of Solar System is described by a metric with constant-curvature background added by astatic perturbation, we show that many f(R) gravities are ruled out by Solar System tests.