The Evolution Of Modified Holographic Ricci Dark Energy In The Brans-dicke Universe

It has been believed that our universe is undergoing an accelerating phase of expansion which is indicated by the cosmological observations,such as Sloan Digital Sky Survey(SDSS),Type Ia supernovae and cosmic microwave background(CMB).As we know,many theoretical researchers explained this phenomenon by assuming the existence of an unknown component,i.e.,an exotic energy with negative pressure,named dark energy.However,it's difficult to understand the nature of this component and this provides a great challenge to scientists.The simplest candidate for the dark energy is the cosmological constant A,but it suffers from some problems.So a number of dark energy models have been constructed.These scenarios include Quintessence,Quintom,Tachyon,Chaplygin gas,etc.All of them have their own advantages and disadvantages.Firstly,in this thesis we will introduce the development of cosmology and then have a brief review of modern cosmology,which includes Big Bang cosmology and its defects,as well as inflation model and its explanation for the defects of Big Bang cosmology model.Afterwards,we overview several common dark energy models.Secondly,in flat Brans-Dicke framework,we study the evolutions of EOS(equation of state)parameter ?de and deceleration parameter q in modified holographic Ricci dark energy(MHRDE)model.When there are interactions not only between the dark energy and dark matter,but also between the gravitational field and material field,the influences of interaction terms for model parameter are discussed.In addition,the results show that the EOS parameter can across the Phantom divide.We discuss the evolutions of EOS parameter with interaction and deceleration parameter in viscous MHRDE model.Considering the viscosity effect,the EOS parameter will across the Phantom divide later.Finally,we study the thermodynamical properties of the MHRDE model with interaction in flat Brans-Dicke framework.The expressions of the second law of thermodynamics and the correction of entropy have been obtained in this model.As the figure illustrates,the second law of thermodynamics are satisfied during the whole evolution.