论文标题
由kalb-ramond田地驱动
Ekpyrotic bounce driven by Kalb-Ramond field
论文作者
论文摘要
我们提出了一个由第二级反对称Kalb-Ramond场驱动的ekpyrotic Bounce场景，该场宇宙最初通过ekpyrototic阶段收缩，具有非单明一角的弹跳行为，因此，它平稳地传播到了扩展的阶段。特别是，KR场通过线性耦合与标量场（来自较高曲率D.O.F）的相互作用。在收缩阶段，KR和标量之间的相互作用能量密度比$ a^{-6} $的增长速度快 - 在遥远的过去具有可忽略的效果，但是随着宇宙继续收缩，这种相互作用能量密度逐渐增长并起着重要的作用，在最低尺度因素的最小值中触发非单调的弹跳起着重要作用。弹跳是对称和ekpyrotic，在宇宙扩展阶段弹跳后弹跳剂的能量密度迅速降低，因此，标准的大爆炸宇宙学被恢复。在这种ekpyrotic弹跳方案中，我们发现曲率扰动在大规模模式上获得了蓝色的倾斜光谱 - 与Planck数据不一致。为了解决这个问题，我们提出了一个扩展的方案，在该方案之前，ekpyrotic阶段之前是准物质占主导地位的前ekpyrotic阶段，然后重新投资扰动功率谱。结果，原始曲率扰动在前卵形阶段越过地平线的尺度上，事实证明几乎是尺度不变的，确实与最近的普朗克数据一致。这项工作的标志是，尽管Kalb-Ramond Field目前的占地面积可忽略不计，但在宇宙的早期阶段，它产生了相当大的影响，这反过来又使宇宙的进化非单星。
We propose an ekpyrotic bounce scenario driven by a second rank antisymmetric Kalb-Ramond field, where the universe initially contracts through an ekpyrotic stage having a non-singular bouncing like behaviour, and consequently, it smoothly transits to an expanding phase. In particular, the KR field has an interaction with a scalaron field (coming from higher curvature d.o.f) by a linear coupling. The interaction energy density between the KR and the scalaron grows faster than $a^{-6}$ during the contraction phase -- which has negligible effects at the distant past, however as the universe continues to contract, this interaction energy density gradually grows and plays a significant role to trigger a non-singular bounce at a minimum value of the scale factor. The bounce being symmetric and ekpyrotic, the energy density of the bouncing agent rapidly decreases after the bounce during the expanding phase of the universe, and consequently the standard Big-Bang cosmology gets recovered. In such ekpyrotic bounce scenario, we find that the curvature perturbation gets a blue tilted spectrum over the large scale modes -- not consistent with the Planck data. To circumvent this problem, we propose an extended scenario where the ekpyrotic phase is preceded by a quasi-matter dominated pre-ekpyrotic phase, and re-investigate the perturbation power spectrum. As a result, the primordial curvature perturbation, at scales that cross the horizon during the pre-ekpyrotic stage, turns out to be nearly scale invariant that is indeed consistent with the recent Planck data. The hallmark of the work is that although the Kalb-Ramond field has negligible footprints at present universe, it has considerable impacts during early stage of the universe, which in turn makes the universe's evolution non-singular.
