Matter instabilities in general Gauss-Bonnet gravity
Matter instabilities in general Gauss-Bonnet gravity
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DOI：
10.1103/physrevd.81.023532
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发表时间：
2009-11
影响因子：
5
通讯作者：
A. D. Felice;D. Mota;S. Tsujikawa
中科院分区：
文献类型：
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作者：
A. D. Felice;D. Mota;S. Tsujikawa
本文研究了f（G）引力中宇宙学扰动的演化，这里的拉格朗日量是Ricci标量R与任意函数f关于Gauss-Bonnet项G的和。我们推导出扰动方程，假设物质由具有常数状态方程w的理想流体描述。我们表明，在理想流体中的密度扰动表现出负的不稳定性，无论在辐射和物质的优势，f（G）的形式。这种扰动的增长在较小的尺度上变得更强，除非与广义相对论的偏差非常小，否则很难与观测到的星系光谱兼容。因此，f（G）宇宙学模型实际上被排除在这种紫外不稳定性之外，尽管它们可以与晚期宇宙加速度和局部重力约束兼容。
We study the evolution of cosmological perturbations in f(G) gravity, where the Lagrangian is the sum of a Ricci scalar R and an arbitrary function f in terms of a Gauss-Bonnet term G. We derive the equations for perturbations assuming matter to be described by a perfect fluid with a constant equation of state w. We show that density perturbations in perfect fluids exhibit negative instabilities during both the radiation and the matter domination, irrespective of the form of f(G). This growth of perturbations gets stronger on smaller scales, which is difficult to be compatible with the observed galaxy spectrum unless the deviation from general relativity is very small. Thus f(G) cosmological models are effectively ruled out from this ultraviolet instability, even though they can be compatible with the late-time cosmic acceleration and local gravity constraints.