论文标题
修改后的高斯骨网宇宙学的延迟限制
Late-time constraints on modified Gauss-Bonnet cosmology
论文作者
论文摘要
在本文中，我们考虑了一个重力动作，其中包含RICCI标量（$ r $）和拓扑高斯（Toopological Gauss）的组合 - bonnet术语，$ g $。具体来说，我们研究了由对称考虑因素选择的特定修改重力理论的宇宙学特征，即$ f（r，g）= r^n g^{1-n} $模型。在空间平坦，均质和各向同性背景的背景下，我们表明可以通过几何形状来解决当前观察到的宇宙的加速度，因此避免了\ emph {de facto}宇宙学常数的缺点。因此，我们提出了一种在没有压力物质的情况下数值求解弗里德曼方程并获得哈勃扩展率的红移行为的策略。然后，为了检查模型的生存能力，我们通过应用于晚期宇宙观察的贝叶斯蒙特卡洛方法对理论的自由参数进行约束。我们的结果表明，$ f（r，g）$模型能够模仿标准$λ$ CDM模型的低频行为，尽管朝着高红移时出现了实质性差异，从而导致缺乏标准的物质主导的时期。最后，我们研究了能量条件，并表明，在适当的选择界面参数的值下，在考虑从我们的分析中获得的$ n $的平均值时，它们都被违反，就像在深色流体的情况下一样。
In this paper, we consider a gravitational action containing a combination of the Ricci scalar, $R$, and the topological Gauss--Bonnet term, $G$. Specifically, we study the cosmological features of a particular class of modified gravity theories selected by symmetry considerations, namely the $f(R,G)= R^n G^{1-n}$ model. In the context of a spatially flat, homogeneous and isotropic background, we show that the currently observed acceleration of the Universe can be addressed through geometry, hence avoiding \emph{de facto} the shortcomings of the cosmological constant. We thus present a strategy to numerically solve the Friedmann equations in presence of pressureless matter and obtain the redshift behavior of the Hubble expansion rate. Then, to check the viability of the model, we place constraints on the free parameters of the theory by means of a Bayesian Monte Carlo method applied to late-time cosmic observations. Our results show that the $f(R,G)$ model is capable of mimicking the low-redshift behavior of the standard $Λ$CDM model, though substantial differences emerge when going toward high redshifts, leading to the absence of a standard matter-dominated epoch. Finally, we investigate the energy conditions and show that, under suitable choices for the values of the cosmographic parameters, they are all violated when considering the mean value of $n$ obtained from our analysis, as occurs in the case of a dark fluid.
