arXiv 1306.19432013-06gr-qcastro-ph.COhep-th

从第五维Brans-Dicke理论看暗能量

Dark Energy From Fifth Dimensional Brans-Dicke Theory

Amir F. Bahrehbakhsh, Mehrdad Farhoudi, Hajar Vakili

备注：: 16 pages, 5 figures, 3 tables
发表信息：: Inter. J. Mod. Phys. D Vol. 22, No. 12 (2013) 1350070 (18 pages)
DOI：: 10.1142/S0218271813500703

摘要：

本文采用诱导物质理论的方法，研究了五维Brans-Dicke理论的宇宙学意义，并提出了解释宇宙加速的理论。在四维超曲面中引入能量-动量张量，将其分为两部分，一部分代表所有的物质（重子物质和暗物质），另一部分包含了第五维标度因子和标量场所产生的所有额外项，我们将其视为暗能量的能量-动量张量。我们还将能量动量守恒方程分解为两个守恒方程，一个是物质守恒方程，另一个是暗能量守恒方程。我们执行此程序的不同情况下，没有相互作用的条款和两个特定的（合适的）相互作用的条款之间的两个部分。假设暗能量状态方程的参数为常数，模型的方程允许幂律解。虽然，非相互作用的情况下不给任何加速宇宙，但相互作用的情况下，既给减速和加速宇宙。在相互作用的情况下，我们解析地给出了模型中某些参数的可接受范围，并进行了数据分析，检验了模型参数值与Union2.1中580 SNe Ia距离模观测数据的一致性。对于其中一种相互作用情况，最佳拟合值表明Brans-Dicke耦合常数（ω）为-7.75，然而，它也给出了暗能量的状态参数（wX）等于-0.67。此外，该模型给出了哈勃和减速参数在目前的H 0 = 69.4（km/s）/Mpc和q 0 = -0.38（在其置信区间内），其中第五维的比例因子随着时间的推移而缩小。

英文摘要：

Following the approach of the induced-matter theory, we investigate the cosmological implications of a five-dimensional Brans-Dicke theory, and propose to explain the acceleration of the universe. After inducing in a four-dimensional hypersurface, we classify the energy-momentum tensor into two parts in a way that, one part represents all kind of the matter (the baryonic and dark) and the other one contains every extra terms emerging from the scale factor of the fifth dimension and the scalar field, which we consider as the energy-momentum tensor of dark energy. We also separate the energy-momentum conservation equation into two conservation equations, one for matter and the other for dark energy. We perform this procedure for different cases, without interacting term and with two particular (suitable) interacting terms between the two parts. By assuming the parameter of the state equation for dark energy to be constant, the equations of the model admit the power-law solutions. Though, the non-interacting case does not give any accelerated universe, but the interacting cases give both decelerated and accelerated universes. For the interacting cases, we figure out analytically the acceptable ranges of some parameters of the model, and also investigate the data analysis to test the model parameter values consistency with the observational data of the distance modulus of 580 SNe Ia compiled in Union2.1. For one of these interacting cases, the best fitted values suggest that the Brans-Dicke coupling constant (ω) is -7.75, however, it also gives the state parameter of dark energy (wX) equal to -0.67. In addition, the model gives the Hubble and deceleration parameters at the present time to be H0 = 69.4 (km/s)/Mpc and q0 = -0.38 (within their confidence intervals), where the scale factor of the fifth dimension shrinks with the time.

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