论文标题
$ f（r）$重力$ k $ - essence晚期现象学
$f(R)$ Gravity $k$-Essence Late-time Phenomenology
论文作者
论文摘要
在这项工作中，我们将研究$ k $ - esses $ f（r）$重力的延迟行为，而没有标量的潜力，在物质和辐射完美液体的情况下。我们通过使用state-Finder函数$ y_h（z）= \ frac {ρ_{de}} {ρ_M^{（0）}} $量化了晚期研究，这是红速度和哈勃速率的函数。通过根据红移和函数$ y_h（z）$适当地重写Friedmann方程，我们使用适当的初始条件进行数值求解，并认真研究了$ k $ - essence高阶动力学术语的效果。正如我们所证明的那样，高阶标量场动力学术语对晚期动力学的影响是根本的，因为缺少暗能量振荡，此外，宇宙学物理量与最新的Planck数据兼容，并且该模型几乎与$λ$冷的暗物质模型无法区分。这与存在振荡的标准$ f（r）$重力案例相反。 Furthermore, by choosing a different set of values of two of the free parameters of the model, and specifically the coefficient of the higher order kinetic term and of the exponent of $R^δ$ appearing in the $f(R)$ action, we demonstrate that it is possible to obtain $ρ_{DE}<0$ for redshifts $z\sim 2-3.8$, which complies phenomenologically with, and seems to explain, the至少在考虑到状态参数的暗能量方程和暗能量密度参数时，同一红移的观察数据，并在$ z \ sim 0 $处获得可行的宇宙演化。
In this work we shall study the late-time behavior of $k$-Essence $f(R)$ gravity without scalar potential, in the presence of matter and radiation perfect fluids. We quantify the late-time study by using the statefinder function $Y_H(z)=\frac{ρ_{DE}}{ρ_m^{(0)}}$, which is a function of the redshift and of the Hubble rate. By appropriately rewriting the Friedmann equation in terms of the redshift and of the function $Y_H(z)$, we numerically solve it using appropriate initial conditions, and we critically examine the effects of the $k$-Essence higher order kinetic terms. As we demonstrate, the effect of the higher order scalar field kinetic terms on the late-time dynamics is radical, since the dark energy oscillations are absent, and in addition, the cosmological physical quantities are compatible with the latest Planck data and also the model is almost indistinguishable from the $Λ$ Cold Dark Matter model. This is in contrast to the standard $f(R)$ gravity case, where the oscillations are present. Furthermore, by choosing a different set of values of two of the free parameters of the model, and specifically the coefficient of the higher order kinetic term and of the exponent of $R^δ$ appearing in the $f(R)$ action, we demonstrate that it is possible to obtain $ρ_{DE}<0$ for redshifts $z\sim 2-3.8$, which complies phenomenologically with, and seems to explain, the observational data for the same redshifts, and also to obtain a viable cosmological evolution at $z\sim 0$, at least when the dark energy equation of state parameter and the dark energy density parameters are considered.
