Study On Cosmological Properties For Four Kinds Of Parametric Dark Energy Models

Astronomical observations in recent years suggest that the current universe is in the midst of an accelerating expansion.But how to explain the accelerating expansion of the universe has been a central issue in cosmology.So far,many theories have been proposed,and the cosmological constant model is the most recognized dark energy model,which utilises the vacuum energy to explain the accelerating expansion.Now,there are plenty kinds of dark energy models are established,and no one is perfect.The main content of this thesis is about the related issues for the four kinds of the parametric dark energy model(PDEM).Firstly,the density parameters and deceleration parameters of the parametric dark energy model are studied when the interaction between dark energy and dark matter is not considered.The results show that the evolution trend of density parameters is consistent with the observation if there is no interaction,and the values of deceleration parameters are positive in the past and negative at the present,which show that our universe are decelerating in the past and accelerating at the present.Next,the evolutions of the related cosmological quantities for PDEM,such as the state parameter,deceleration parameter and density parameter,in the flat universe between Dark Energy(DE)and Dark Matter(DM)when the interaction term is Q1= 3?H?de?+1/?dm? and Q2 =3?H ?de?dm/?de+?dm.Finally,on the basis of the above discussions,we make a geometric diagnosis of these parametric dark energy models.Concretely,the state finder and Om geometrical diagnostics in the two different interaction forms are studied,and the standard cosmological model are taken to compare with the standard cosmological model.