Cuscuta-Galileon cosmology: Dynamics, gravitational constants, and the Hubble constant
Cuscuta-Galileon cosmology: Dynamics, gravitational constants, and the Hubble constant
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DOI：
10.1103/physrevd.105.104022
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发表时间：
2022-02
影响因子：
5
通讯作者：
K. Maeda;Sirachak Panpanich
中科院分区：
文献类型：
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作者：
K. Maeda;Sirachak Panpanich
我们基于库斯库塔-伽利略引力理论讨论宇宙学，该理论仅保留两个自由度。尽管不存在额外的自由度，但标量场势的引入改变了动力学。标量场完全由物质场决定。以指数势为例，我们讨论宇宙动力学。有效弗里德曼方程中出现的引力“常数”$G_{\rm F}$ 变得与时间相关。我们还介绍了当我们知道哈勃参数的演化时如何构造势。当我们假设 $\Lambda$CDM 宇宙学作为背景演化时，我们找到了潜在的形式。然后我们分析密度扰动，该方程仅通过引力“常数”$G_{\rm eff}$ 的变化来表征，该变化也与时间相关。从大爆炸核合成的约束和引力常数随时间变化的约束等观测约束出发，我们限制了模型中的参数。考虑到有效弗里德曼方程中引力常数的时间依赖性，我们或许有机会解释哈勃张力问题。
We discuss cosmology based on a Cuscuta-Galileon gravity theory, which preserves just two degrees of freedom. Although there exists no additional degrees of freedom, introduction of a potential of a scalar field changes the dynamics. The scalar field is completely determined by matter fields. Giving an exponential potential as an example, we discuss the cosmological dynamics. The gravitational"constant"$G_{\rm F}$ appeared in the effective Friedmann equation becomes time dependent. We also present how to construct a potential when we know the evolution of the Hubble parameter. When we assume the $\Lambda$CDM cosmology for the background evolution, we find the potential form. We then analyze the density perturbations, which equation is characterized only by a change of the gravitational"constant"$G_{\rm eff}$, which also becomes time dependent. From the observational constraints such as the constraint from the big-bang nucleosynthesis and the constraint on time-variation of gravitational constant, we restrict the parameters in our models. Taking into account the time dependence of the gravitational constant in the effective Friedmann equation, we may have a chance to explain the Hubble tension problem.