标题： 尘埃宇宙中的不均匀性——暗能量的一种可能替代方案？ 显示英文标题

标题： Inhomogeneities in dusty universe - a possible alternative to dark energy?

摘要： 最近，关于非均匀性在解释宇宙观测到的晚期加速中的作用出现了新的争论。 我们借助众所周知的球对称但非均匀的勒梅特-托尔曼-邦迪(LTB)模型，并将其推广到高维空间，进行了分析研究。 观察发现，与Kolb等人提出的观点相反，如果物质场满足能量条件，那么非均匀性的存在以及额外维度都不能改变减速参数的符号。 众所周知的雷乔德希方程也指向相同的结果。 然而，无需显式求解场方程，可以证明尽管总减速是正的，但并不排除在纯尘埃宇宙中存在径向加速的可能性，只要角尺度因子足够快地减速，反之亦然。 此外，发现引入额外维度不能改变这种情形。相反，它实际上有助于减速过程。 显示英文摘要

摘要： There have been of late renewed debates on the role of inhomogeneities to explain the observed late acceleration of the universe. We have looked into the problem analytically with the help of the well known spherically symmetric but inhomogeneous Lemaitre-Tolman-Bondi(LTB) model generalised to higher dimensions. It is observed that in contrast to the claim made by Kolb et al the presence of inhomogeneities as well as extra dimensions can not reverse the signature of the deceleration parameter if the matter field obeys the energy conditions. The well known Raychaudhuri equation also points to the same result. Without solving the field equations explicitly it can, however, be shown that although the total deceleration is positive everywhere nevertheless it does not exclude the possibility of having radial acceleration, even in the pure dust universe, if the angular scale factor is decelerating fast enough and vice versa. Moreover it is found that introduction of extra dimensions can not reverse the scenario. To the contrary it actually helps the decelerating process.