解释宇宙加速膨胀的爱因斯坦—嘉当理论模型

During the last years, the observations of Type Ia Supernovae, Cosmic Microwave Background Radiation and Large Scale Structure of the universe have shown that our universe is undergoing a progress of the accelerated expansion. Dark energy and the modified gravity theory are tried to explain the accelerating universe. So far, many dark energy models and the modified gravity models have been established to explain the phenomenon, but unfortunately, these models can not perspectively explain the acceleration of our universe..Our purpose is to study the problem of the accelerated expansion based on the frame of the Poincaré gauge theory. In our work, firstly we will derive the cosmic term in the Einstein-Cartan theory; secondly we will study the possibility of considering the cosmic term in the Einstein-Cartan theory as dark energy; lastly we will investigate the cosmic term in the Einstein-Cartan theory from the view of the observations. .The problem of the accelerating universe has become one of the most attracting researching area in modern cosmology. The unknown properties of dark energy cause us to study some basic theories necessarily. And perhaps explaining the accelerating universe from these theories could provide the researchers some valuable idea, method and suggestion.

近年来，天文学家通过对Ia型超新星、宇宙微波背景辐射和宇宙大尺度结构等观测实验发现，我们的宇宙正在经历加速膨胀阶段。目前，理论学家主要从两个方面解释这种现象，包括暗能量和修改的引力理论。令人遗憾的是，迄今为止还没有证据表明存在一个理论可以合理地解释宇宙的加速膨胀现象。.本项目旨在从规范引力理论中尽可能找到一个关于这种现象的合理解释。研究作为庞加莱规范理论的最简单形式，爱因斯坦-嘉当理论里的宇宙项作为暗能量的可行性。我们将分三个步骤进行研究：1.推导出爱因斯坦-嘉当理论的宇宙项；2.理论研究此宇宙项作为暗能量的可行性；3.与最新的天文观测数据拟合，研究此宇宙项作为暗能量的可行性。这一问题的解决，即从基础理论解释宇宙的加速膨胀或许可以提供给未来的研究者一些有价值的思路、方法和启示。

在规范引力理论框架下研究宇宙的演化问题，可以为解释宇宙的加速膨胀现象提供合理的理论支持。本项目找到了爱因斯坦-嘉当理论框架下的宇宙动力学演化方程中的宇宙项。将宇宙项类比成Chevallier-Polarski-Linder（CPL）参数化的暗能量形式，研究发现，在选取适当取值的参数情况下，演化方程可以描述宇宙由减速到加速的膨胀过程。采用最新的天文观测数据，与推导给出的理论模型拟合。研究发现，最新的天文观测支持了爱因斯坦-嘉当理论模型中宇宙项作为CPL参数化暗能量的可行性。