最近，在龚（\em et al）的\cite{GWW07}和王（Wang）与桑托斯（Santos）的\cite{WS07}中，通过在$S^{1}/Z_{2}$上的M理论和弦论的框架中使用大额外维，证明了两个轨道膜中的每一个上的有效宇宙学常数可以很容易地降低到它当前的观测值。本文利用\cite{WS07}中的公式研究了宇宙的当前加速度。我们首先构造显式的时间依赖的解决方案的10维体积的Neveu-Schwarz/Neveu-Schwarz部门，紧化的5维环面。然后，我们写下来的两个动力学膜的广义弗里德曼方程，并拟合模型的182金超新星Ia数据和BAO参数从SDSS，使用我们的ECOSTIT和蒙特卡洛马尔可夫链（MCMC）代码。以最佳拟合的参数值为初始条件，对广义Friedmann方程进行数值积分，得到宇宙的未来演化。我们发现这取决于膜的放射子势$V_{4}^{(I)} (I = 1, 2)$的选择。特别是，当选择它们作为Goldberger-Wise势$V_{4}^{(I)} = λ_{4}^{(I)} (ψ^{2} - {v_{I}}^{2})^{2}$时，我们发现由有效宇宙学常数驱动的当前宇宙加速只是暂时的。由于势的影响，宇宙最终将再次进入减速膨胀阶段。我们还研究了两个膜之间的适当距离，并发现在所有考虑的模型中，它在宇宙的整个未来演化过程中几乎保持不变。
英文摘要：
Recently, in Gong {\em et al} \cite{GWW07} and Wang and Santos \cite{WS07} it was shown that the effective cosmological constant on each of the two orbifold branes can be easily lowered to its current observational value, by using the large extra dimensions in the framework of both M-Theory and string theory on $S^{1}/Z_{2}$. In this paper, we study the current acceleration of the universe, using the formulas developed in \cite{WS07}. We first construct explicitly time-dependent solution to the 10-dimensional bulk of the Neveu-Schwarz/Neveu-Schwarz sector, compactified on a 5-dimensional torus. Then, we write down the generalized Friedmann equations on each of the two dynamical branes, and fit the models to the 182 gold supernova Ia data and the BAO parameter from SDSS, using both of our MINUIT and Monte-Carlo Markov Chain (MCMC) codes. With the best fitting values of the parameters involved as initial conditions, we integrate the generalized Friedmann equations numerically and find the future evolution of the universe. We find that it depends on the choice of the radion potentials $V_{4}^{(I)} (I = 1, 2)$ of the branes. In particular, when choosing them to be the Goldberger-Wise potentials, $V_{4}^{(I)} = λ_{4}^{(I)} (ψ^{2} - {v_{I}}^{2})^{2}$, we find that the current acceleration of the universe driven by the effective cosmological constant is only temporary. Due to the effects of the potentials, the universe will be finally in its decelerating expansion phase again. We also study the proper distance between the two branes, and find that it remains almost constant during the whole future evolution of the universe in all the models considered.
