Viable cosmology in bimetric theory
Viable cosmology in bimetric theory
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DOI：
10.1088/1475-7516/2014/06/037
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发表时间：
2014-03
影响因子：
6.4
通讯作者：
A. D. Felice;A. Gumrukcuoglu;S. Mukohyama;Norihiro Tanahashi;Takahiro Tanaka
中科院分区：
文献类型：
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作者：
A. D. Felice;A. Gumrukcuoglu;S. Mukohyama;Norihiro Tanahashi;Takahiro Tanaka
本文研究了双度规理论中的宇宙学微扰，其中两种流体分别耦合到两个度规中的一个。通过对背景解的一个健康分支的讨论，我们阐明了宇宙学扰动的稳定性。为了这个目的，我们延长了所谓的Higuchi鬼的情况下的条件，并表明，该条件是保证满足健康的分支。我们还计算了扰动的平方传播速度，并推导出梯度不稳定性的条件。为了避免梯度不稳定性，我们发现模型参数是弱约束的。
We study cosmological perturbations in bimetric theory with two fluids each of which is coupled to one of the two metrics. Focusing on a healthy branch of background solutions, we clarify the stability of the cosmological perturbations. For this purpose, we extend the condition for the absence of the so-called Higuchi ghost, and show that the condition is guaranteed to be satisfied on the healthy branch. We also calculate the squared propagation speeds of perturbations and derive the conditions for the absence of the gradient instability. To avoid the gradient instability, we find that the model parameters are weakly constrained.