Study Of Quintom Dark Energy Model In Spinor Field

Inflation and dark energy,both of which describe the accelerating expansions in the universe,are two hot issues of modern cosmology,the fitting for the cosmological data have well supported that the interpretation that dark energy drives the present accelerating expansion of our universe.Besides,inflation and the existence of dark energy also supported by the new publicized data by the five-year WMAP observation.The kind of matter with negative pressure,which drive the late time acceleration and is large-scale isotropy and homogeneity distributing and not interacting with gravity,dominates the our modern universe-accounts for over two out of there all compoments.Furthermore,it may have effect on the evolution of oue universe.So it is reckoned that what is the nature of the dark energy and how it will influence the evolvement of the universe.In the literature there are various proposals for the theoretical models of the dark energy,such as the cosmological constant, Holographic dark energy,Agegraphic and other dynamical models like Quintessence, Phantom,K-essence,Quintom,and so on.The cosmological observations indicate that the behavior of dark energy is in consistency with a cosmological constant,however,some theoretical difficulties are still presents in this model.Naturally we may take the dynamical dark energy scenarios into consideration,and one class of models with an equation of state crossing the cosmological constant boundary——Quintom,is mildly favored.The existing Quintom models include real and complex scalar models,vector interacting dark energy model,Spinor Quintom,modified gravity models,etc.In this thesis I will focus on theoretical discussions of Quintom model in spinor scenario.Firstly,I shall briefly review on the supports by observations and the background of theoretical Quintom dark energy model. Secondly,by taking certain form of potential,I realize a new Quintom model-Spinor Quintom-to explain the behavior of crossing -1 with equation of state in recent evolution.For the first part,I present classes of Spinor Quintom models,we can see either of them can evolve to a De Sitter phase.Secondly,some characters,for instance,duality,statefinder,and the acting as a perfect fluid,will be considered.By these investigations,I established the relations between these models and dishtinguished them by Statefinder parameter.I also realize the unification from matter dominated period to dark energy universe,which finally evolve to a de Sitter spacetime,resolving the evolution from matter dominated period to dark energy dominant universe.Taking dark matter for consideration,we can see that the fraction of density between the two components was an exact constant from the beginning,and evolve,along with the expantion of the scale factor,to equal to each other then to current propotion,ite.24%of dark matter and 72%of dark energy,which accouts for the "coincidence problem" and further relieve the "fine-tuning problem".In the last part of my discussions,I will discuss the thermodynamics of Spinor Quintom model.I investigate the validity of the generalized second law of thermodynamics under certain conditions,as well as stabilities of thermodynamics of the combination between Quintom model with spinor field and the generalized Chapylin Gas perfict fluid.I find that under certain temperatue,this thermal system is stable.