Dark Energy Models And Their Analysis And Comparison

Astronomy in the last century has achieved great progress. From Albert Einstein proposed General Relativity and applied it to the cosmology, to Hubble found cosmic expansion, Gamow proposed the big bang theory, Wilson and Penzias found the cosmic microwave background radiation, then in 1998, two supernova group found the acceleration of the universe's expansion, dark energy, who accounts for 73 percent of the total energy of the cosmos, immediately became a hotspot and focused the cosmological research. Beginning with background knowledge of the universe accelerating expansion, dark energy and type la supernovae, we mainly introduce the cosmological constant model, holographic dark energy model and several kinds of classic dynamic dark energy models such as Quintessence, Phantom, Quintom, Tachyon, Chaplygin Gas, and qualitatively analyze the advantages and disadvantages of various models. The cosmological constant model though formally straightforward, and consistent with the observation very well, but being a slight blemish, there still exists both fine tunning problem and coincidence problem The state equation of Quintessence dark energy, being differ from the state equation of cosmological constant model which is a constant, is variable between the interval of (-1,+ 1). And in this model, there is not coincidence problem Phantom dark energy model is similar to Quintessence, but it solves the shortcomings that the state equation may traverse through -1, which can lead to the Big Rip. Quintom dark energy model is the synthsis of Quintessence and Phantom, it simultaneously possesses some properties of both two kinds of models. Holographic dark energy model, whose state equation only contains one parameter c and can can change nearby-1, is based on the holographic principle of quantum mechanics.Because of the variety of present dark energy models, we urgently need to find a method to identify and analyze the models. Statefinder is such a kind of method. By introducing the Statefinder parameters on {r, s}, the basic idea of Statefinder is to contract the distance in s-r plane between dark energy models and the fixed point {0,1} i.e. A CDM model. Using this method, Chaplygin Gas and Holographic dark energy models are analysised and compared, s-r relations of Modified Chaplygin Gas dark energy model and Generalized Gas Chaplygin dark energy model with dust were deeply studied, and the evolution behaviors of the aforementioned dark energy models in s-r plane were given in this paper.