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arXiv 1802.02728gr-qcastro-ph.COhep-phhep-th
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超越Horndeski引力理论中与GW170817一致的暗能量方案

Dark energy scenario consistent with GW170817 in theories beyond Horndeski gravity

Ryotaro Kase, Shinji Tsujikawa

备注：
23 pages, 7 figures, published version
发表信息：
Phys. Rev. D 97, 103501 (2018)
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摘要：

四阶Gleyzes-Langlois-Piazza-Vernizzi（GLPV）理论是标量张量理论的一般框架，它允许在各向同性宇宙学背景下实现张量传播速度$c_t$等于1。我们提出了一个暗能量模型，在该模型中，晚期宇宙加速发生在一个简单的k-本质拉格朗日类似的鬼凝聚与立方和四次Galileons在GLPV理论的框架。我们表明，各种各样的变化的暗能量状态方程$w_{\rm DE}$包括进入区域$w_{\rm DE}<-1$可以实现不违反条件的鬼和拉普拉斯不稳定性的情况下。由于存在一个二次k-本质拉格朗日量$X^2$，避免了对物质时代跟踪状态方程$w_{\rm DE}=-2$的逼近，这一方法不受观测数据的支持.研究了$c_t^2=1$模型中非相对论性物质扰动的演化，证明了分别与牛顿引力势和弱引力透镜势有关的两个量$μ$和$Σ$实际上是等价的，使得$μ\simeq Σ>1$ .对于其中的偏差$w_{\rm DE}$从$-1$是显着的情况下，在较晚的宇宙学时期，$μ$和$Σ$的值往往是较大的低红移。我们还发现我们的暗能量模型可以与Horndeski理论中由于大质量天体内部引力定律的修正而产生的偏差参数$α_{\rm H}$的界限相一致。

英文摘要：

The Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories up to quartic order are the general scheme of scalar-tensor theories allowing the possibility for realizing the tensor propagation speed $c_t$ equivalent to 1 on the isotropic cosmological background. We propose a dark energy model in which the late-time cosmic acceleration occurs by a simple k-essence Lagrangian analogous to the ghost condensate with cubic and quartic Galileons in the framework of GLPV theories. We show that a wide variety of the variation of the dark energy equation of state $w_{\rm DE}$ including the entry to the region $w_{\rm DE}<-1$ can be realized without violating conditions for the absence of ghosts and Laplacian instabilities. The approach to the tracker equation of state $w_{\rm DE}=-2$ during the matter era, which is disfavored by observational data, can be avoided by the existence of a quadratic k-essence Lagrangian $X^2$. We study the evolution of nonrelativistic matter perturbations for the model $c_t^2=1$ and show that the two quantities $μ$ and $Σ$, which are related to the Newtonian and weak lensing gravitational potentials respectively, are practically equivalent to each other, such that $μ\simeq Σ>1$. For the case in which the deviation of $w_{\rm DE}$ from $-1$ is significant at a later cosmological epoch, the values of $μ$ and $Σ$ tend to be larger at low redshifts. We also find that our dark energy model can be consistent with the bounds on the deviation parameter $α_{\rm H}$ from Horndeski theories arising from the modification of gravitational law inside massive objects.

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