The Dynamic Evolutions Of The Modified Chaplygin Gas And The Generalized Hobbit Model And Some Impacts On The Cosmic Structure Formation

In recent years, many observations from SNe Ia indicate that the expansion ofthe universe is currently accelerating, also along with the observations of CMBRanisotropy spectrum and large scale structure (LSS). These results strongly implythe existence of a dubbed component with negative pressure, which is named asdark energy. It permeates homogenously in all the universe and pushes the ac-celerated expansion of the universe. Although dark energy has been preliminarilyknown, its nature still remains an open and fascinating problem. Dark energyhas become one of the most important problems for the research of contemporaryphysics and cosmology. In this thesis, we first introduce the elementary theory ofthe modern cosmology and some popular dark energy models based on standardcosmology. In the following, the discussions are mainly focused on unified dynamicmodels. Based on our previous work for the MCG model, we continue to studythe evolutional trends of the energy density, energy transfer as well as the growthindex. By analysis, it is found that the evolution of the universe in the MCGmodel is consistent with current observations if the proper parameters are chosen.Then we attempt to use a unified phenomenological model to explain the acceler-ated expansion of the universe. Concretely, on the basis of the Hobbit model, weextend the method of V.F.Cardone to a more general phenomenological model,i.e. the generalized Hobbit model. The main purpose is to make this model cannot only mimic theΛCDM model after the pressureless matter starts to dominatethe universe, but also describe a four-phase smooth transition of the universe,namely the in?ationary phase, a radiation-dominated phase, a matter-dominatedphase and a de Sitter-like phase. In order to check whether this model is a viableone, the evolution of the universe is discussed. Here we respectively discuss thetwo cases with and without interaction. Moreover, the structure formation is sim-ply discussed by the comparison with theΛCDM model. It is obvious that thegeneralized Hobbit model is fit to the current observations, as intended.