Pre-inflationary universe in loop quantum cosmology
Pre-inflationary universe in loop quantum cosmology
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循环量子宇宙学中的暴胀前宇宙
DOI：
10.1103/physrevd.96.083520
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发表时间：
2017
影响因子：
5
通讯作者：
Sheng Qin
中科院分区：
文献类型：
--
作者：
Zhu Tao;Wang Anzhong;Cleaver Gerald;Kirsten Klaus;Sheng Qin
在 LQC 的修饰度量方法中系统地研究了平坦 FLRW 宇宙的演化及其线性扰动。当它由量子弹跳时暴胀子的动能主导时，背景的演化可以在预热之前分为三个不同的阶段，即弹跳、过渡和慢滚暴胀。在反弹阶段，演化不仅与初始条件无关，而且与通货膨胀潜力无关。特别是，在所有考虑的情况下，扩展因子可以通过相同的精确解来很好地描述。相反，在潜在主导的情况下，这种普遍性就消失了。正是由于这种普遍性，线性扰动也独立于暴胀模型并且能够准确获得。在过渡阶段，背景的演变及其线性扰动被明确地发现，然后与其他两个阶段中给出的相匹配。因此，一旦施加初始条件，线性标量和张量扰动将被唯一确定。考虑两组不同的初始条件，一组在收缩阶段施加，另一组在反弹阶段施加，我们计算了 Bogoliubov 系数，发现这两组产生相同的结果，并且都导致在暴胀开始时产生粒子。由于暴胀前的动力学，标量和张量功率谱变得与尺度相关。与普朗克 2015 年的数据相比，我们发现宇宙自反弹以来必须膨胀的总 e 折叠数受到限制，以便与当前的观测结果保持一致。
The evolutions of the flat FLRW universe and its linear perturbations are studied systematically in the dressed metric approach of LQC. When it is dominated by the kinetic energy of the inflaton at the quantum bounce, the evolution of the background can be divided into three different phases prior to the preheating, {\em bouncing, transition and slow-roll inflation}. During the bouncing phase, the evolution is independent of not only the initial conditions, but also the inflationary potentials. In particular, the expansion factor can be well described by the same exact solution in all the cases considered. In contrast, in the potential dominated case such a universality is lost. It is because of this universality that the linear perturbations are also independent of the inflationary models and obtained exactly. During the transition phase, the evolutions of the background and its linear perturbations are found explicitly, and then matched to the ones given in the other two phases. Hence, once the initial conditions are imposed, the linear scalar and tensor perturbations will be uniquely determined. Considering two different sets of initial conditions, one imposed during the contracting phase and the other at the bounce, we calculate the Bogoliubov coefficients and find that the two sets yield the same results and all lead to particle creations at the onset of the inflation. Due to the pre-inflationary dynamics, the scalar and tensor power spectra become scale-dependent. Comparing with the Planck 2015 data, we find constraints on the total e-folds that the universe must have expanded since the bounce, in order to be consistent with current observations.