Cosmological Observations And Dark Energy Models

Cosmology is experiencing a precise epoch since the last decade of twentieth century anddark energy is one of the most important challenges on physics and astronomy. In order todiscover the mysterious nature of dark energy, scientists study dark energy from two side:physical mechanism and observational view. This thesis mainly focus on the reconstructionof dark energy in our really four-dimension world and a five-dimension Ricci flat model witha model independent method and its influence on the universe evolution.In this thesis, firstly, the background of cosmology and the standard cosmological modelare reviewed, then, some of the cosmological observations, dark energy models and recon-struction of dark energy are also briefly introduced. Two parameterized equation of state ofdark energy were constrained from recent observations as three acceleration parameter forms.The effect of models and observational data is explored.Dark energy in a five-dimension Ricci flat big bounce model has been studied. In thismodel, the universe is a hypersurface embedded in a Ricci flat five-dimensional manifold whichis empty or vacuum from the higher dimensional view. But, from four-dimensional view, itis full of matter induced from the extra dimension, named induced matter. The arbitraryfunction f(z) in this model could be found from the equation of dark energy constrained fromobservations, in this way, the model can be reconstructed and its evolution is determined.