作为外禀曲率和空间曲率函数的宇宙学常数
The Cosmological Constant as a Function of Extrinsic Curvature and Spatial Curvature
摘要：
本文假设当宇宙膨胀时，宇宙学常数也会发生变化。一般认为，宇宙学常数是尺度因子和哈勃常数的函数。根据ADM公式，对于FRW度量，非固有曲率$I$等于$-6H^{2}$，空间曲率$R$等于$6k/a^{2}$。因此我们假设宇宙学常数是外曲率和空间曲率的函数。我们在这些模型中研究了FRW宇宙的宇宙学演化。最后我们研究了两个能很好地拟合观测数据的特殊的暗能量模型。实际上，不变的宇宙学常数并不是必需的。如果宇宙膨胀时，宇宙学常数变化缓慢，并逐渐趋于常数，那么暗能量的观测数据也可以用这种理论很好地拟合。
英文摘要：
In this paper we suppose that the cosmological constant will change when the universe expends. For a general consideration, the cosmological constant is assumed to be a function of scale factor and Hubble constant. According to the ADM formulation, to the FRW metric, the extrinsic curvature $I$ equals $-6H^{2}$ and spatial curvature $R$ equals $6k/a^{2}$. Therefore we suppose cosmological constant is a function of extrinsic curvature and spatial curvature. We investigate the cosmological evolution of FRW universe in these models. At last we investigate two particular models which could fit the observation data about dark energy well. Actually a changeless cosmological constant is not essential. If when the universe expands, the cosmological constant changes slowly and gradually flows to a constant, the observation data about dark energy could also be fitted well by this kind of theory.
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