The Dark Energy Models And Thermodynamic Description In The Brans-Dicke Theory

Resent years, observations of type la super-novae, accurate date on the cosmic microwave background and large-scale structure analysis showed that our universe is at the stage of ac-celerating.How to explain the accelerated expansion of the universe become one of the popular questions. There are two main theory to explain the problem, one of them is to consider modi-fied theories of gravity which essentially is to modify the part of geometry in Einstein’s equa-tion; another one is to introduce an exotic component with large negative pressure named dark energy, which can provide the exclusion which counteract the gravitation.There are a variety of models of dark energy to explain the expansion of our universe, they have their own advantage or weakness.In this paper, we first introduce the background knowledge of modern cosmology, dark en-ergy models as well as the basic knowledge of black hole thermodynamics. And then described holographic dark energy model and new agegraphic dark energy model in Brans-Dicke theory, given the equations of state parameter and deceleration parameter of these two models, respec-tively. After analysis we found that for these two models in the Brans-Dicke theory, if we select the appropriate parameters that the phantom crossing can be constructed. Not only are they better able to accelerate the expansion of the universe, but also returned to the form of Einstein theory. The effect of interaction between dark energy and dark matter is thermodynamically interpreted as a small fluctuation around the thermal equilibrium. Therefor we analysis them in thermodynamics. A relation between the interaction term of the dark components and thermal fluctuation is obtained. Also the relation can returned to the form of Einstein theory.