论文标题
$ f（r）$重力各向同占反弹前的承包宇宙吗？
Can $f(R)$ gravity isotropize a pre-bounce contracting universe?
论文作者
论文摘要
我们解决了在$ f（r）$重力中反弹前缔约阶段各向同性化的重要问题，这对于在$ f（r）$重重中构建任何可行的非弹力弹跳方案都是相关的。这项工作背后的主要动机是研究$ f（r）$重力本身是否可以同时发生的宇宙最初从小各向异性开始而不掺入超级Stift或非理想的液体，这是不可能的，这通常是不可能的。考虑到Bianchi I宇宙学和采用动力学系统分析，我们看到$ r^n $（$ n> 1 $）和$ r+r+αr^2 $（$α> 0 $）理论是不可能的，但对于$ \ frac {1}αee^αe^{αr} $（$α> 0 $）。另一方面，如果一个人没有指定先验的$ f（r）$理论，但要求宇宙学平稳地将ekpyrotic收缩阶段连接到非弹力，则ekpyrototo阶段\ emph {may}却不满足同型和物理性易于稳定性的条件。
We address the important issue of isotropisation of a pre-bounce contracting phase in $f(R)$ gravity, which would be relevant to construct any viable nonsingular bouncing scenario in $f(R)$ gravity. The main motivation behind this work is to investigate whether the $f(R)$ gravity, by itself, can isotropise a contracting universe starting initially with small anisotropy without incorporating a super-stiff or non-ideal fluid, that is impossible in general relativity. Considering Bianchi I cosmology and employing a dynamical system analysis, we see that this is not possible for $R^n$ ($n>1$) and $R+αR^2$ ($α>0$) theory, but possible for $\frac{1}αe^{αR}$ ($α>0$) theory. On the other hand, if one does not specify an $f(R)$ theory a priori but demands a cosmology smoothly connecting an ekpyrotic contraction phase to a nonsingular bounce, the ekpyrotic phase \emph{may} not fulfil the condition for isotropisation and physically viability simultaneously.
