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arXiv 1708.04823gr-qcastro-ph.CO
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具有暴胀和晚期加速的简单宇宙学模型

Simple cosmological model with inflation and late times acceleration

Marek Szydlowski, Aleksander Stachowski

摘要:

在多项式Palatini宇宙学的框架下,我们研究了一个简单的爱因斯坦坐标系下的均匀各向同性宇宙模型。我们发现在这个模型中,宇宙演化过程中出现了早期的暴胀和晚期的膨胀加速阶段。在此框架下,我们得到了具有标量场形式的物质和暗能量的Friedmann方程,其势的形式由FRW度规的Ricci标量以协变的方式确定。物质和暗能量的能量密度也通过Ricci标量参数化。早期的暴胀只在物质的能量密度的极小部分时才能得到。物质与暗能量之间存在相互作用,因为暗能量是衰减的。为了刻画暴胀,我们用Ricci标量计算了慢滚参数和常滚参数。我们发现了暗能量密度随宇宙时间变化的一个特征行为,它遵循logistic-like曲线,该曲线插入两个几乎恒定值的相位。从所需的$N$ -折叠数中,我们发现了模型参数的一个界限。

英文摘要:

In the framework of polynomial Palatini cosmology, we investigate a simple cosmological homogeneous and isotropic model with matter in the Einstein frame. We show that in this model during cosmic evolution, it appears the early inflation and the accelerating phase of the expansion for the late times. In this frame we obtain the Friedmann equation with matter and dark energy in the form of a scalar field with the potential whose form is determined in a covariant way by the Ricci scalar of the FRW metric. The energy density of matter and dark energy are also parametrized through the Ricci scalar. The early inflation is obtained only for an infinitesimally small fraction of energy density of matter. Between the matter and dark energy, there exists interaction because the dark energy is decaying. For characterization of inflation we calculate the slow roll parameters and the constant roll parameter in terms of the Ricci scalar. We have found a characteristic behaviour of the time dependence of density of dark energy on the cosmic time following the logistic-like curve which interpolates two almost constant value phases. From the required numbers of $N$-folds we have found a bound on model parameter.

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