变减速参数弦宇宙学中的各向异性Bianchi-I宇宙学模型
Anisotropic Bianchi-I Cosmological Models in String Cosmology with Variable Deceleration Parameter
摘要：
本文研究了空间均匀各向异性的大质量弦Bianchi-I宇宙模型。Letelier（Phys.Rev.D28：2414，1983）提出的能量-动量张量已被用来构造有质量的弦宇宙学模型，我们假定模型中的膨胀标量正比于剪切张量的一个分量。通过考虑与时间有关的减速参数，求解了爱因斯坦场方程，该减速参数使得标度因子$a = (\sinh(αt))^{\frac{1}{n}}$，其中$α$和$n$是常数。结果表明，对于$n > 1$，该模型描述了宇宙从早期减速阶段向近期加速阶段的转变，而对于$0 < n \leq 1$，该模型描述了宇宙的纯加速阶段，这与近期的天体物理观测结果一致.此外，还详细讨论了模型的一些物理和几何性质以及解的物理可接受性。
英文摘要：
The present study deals with spatially homogeneous and anisotropic Bianchi-I cosmological model representing massive strings. The energy-momentum tensor, as formulated by Letelier (Phys. Rev. D 28: 2414, 1983) has been used to construct massive string cosmological model for which we assume that the expansion scalar in the model is proportional to one of the components of shear tensor. The Einstein's field equations have been solved by considering time dependent deceleration parameter which renders the scale factor $a = (\sinh(αt))^{\frac{1}{n}}$, where $α$ and $n$ are constants. It has been detected that, for $n > 1$, the presented model has a transition of the universe from the early decelerated phase to the recent accelerating phase at present epoch while for $0 < n \leq 1$, this describes purely accelerating universe which is consistent with recent astrophysical observations. Moreover, some physical and geometric properties of the model along with physical acceptability of the solutions have been also discussed in detail.
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