arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0705.3795gr-qcastro-phhep-ph
收藏

修正的Gauss-Bonnet引力的宇宙学

The Cosmology of Modified Gauss-Bonnet Gravity

Baojiu Li, John D. Barrow, David F. Mota

备注：
10 pages, 4 figures. Referenes updated; to appear in Phys. Rev. D
发表信息：
Phys.Rev.D76:044027,2007
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

我们考虑的宇宙学中的高斯-邦纳项G的一些函数f（G）被添加到引力作用，以说明宇宙的后期加速膨胀。用一种同样适用于一般f（R，R^abR_ab，R^abcdR_abcd）引力理论的方法导出了协变和规范不变微扰方程。我们指出，尽管f（G）引力模型具有四阶性质，但它们一般不能再现任意背景宇宙演化;例如，标准LCDM范式（Omega_DE = 0.76）不能在f（G）引力理论中实现，除非f是一个真正的宇宙学常数，因为它对f（G）的形式施加了排斥性约束。我们分析了扰动方程，发现与f（R）模型一样，扰动增长的稳定性对f（G）的函数形式有一定的限制，此时d^2 f/dG^2 < 0.此外，小尺度扰动的稳定性还要求f不显著偏离常数。这些分析说明了数值传播的微扰方程与一个特定的模型再现一个有代表性的LCDM宇宙历史。我们的结果表明，f（G）模型是如何高度约束的宇宙学数据。

英文摘要：

We consider the cosmology where some function f(G) of the Gauss-Bonnet term G is added to the gravitational action to account for the late-time accelerating expansion of the universe. The covariant and gauge invariant perturbation equations are derived with a method which could also be applied to general f(R,R^abR_ab,R^abcdR_abcd) gravitational theories. It is pointed out that, despite their fourth-order character, such f(G) gravity models generally cannot reproduce arbitrary background cosmic evolutions; for example, the standard LCDM paradigm with Omega_DE = 0.76 cannot be realized in f(G) gravity theories unless f is a true cosmological constant because it imposes exclusionary constraints on the form of f(G). We analyze the perturbation equations and find that, as in f(R) model, the stability of early-time perturbation growth puts some constraints on the functional form of f(G), in this case d^2 f/d G^2 < 0. Furthermore, the stability of small-scale perturbations also requires that f not deviate significantly from a constant. These analyses are illustrated by numerically propagating the perturbation equations with a specific model reproducing a representative LCDM cosmic history. Our results show how the f(G) models are highly constrained by cosmological data.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑