论文标题
有限的奇异性弹跳宇宙
Bounce universe with finite-time singularity
论文作者
论文摘要
这项工作解释了IV型奇点（轻度奇异性）的存在如何影响弹跳宇宙的动态。特别是，我们研究了在幽灵自由高斯重力理论的背景下以IV奇异性出现的弹跳宇宙学。根据IV型奇异性的发生时间，可能会出现三种不同的情况 - 当奇异性分别发生在弹跳之前或弹跳之前或弹跳的瞬间时。但是，在所有这些情况下，我们发现，在“全球”奇异性影响时空时，标量功率谱变成红色倾斜，张量表与尺度比率太大，无法与观察数据一致。基于这些发现，我们研究了一种不同的弹跳场景，该场景也以IV型奇异性出现，并且奇异性会影响到发生时的时空“本地”。结果，与以前的方案不同，第二种反弹方案中的扰动模式可能会在深度缔约阶段远离反弹。最终，这导致可观察量与普朗克数据的同时兼容，并确保弹跳模型的可行性，其中类型IV奇异性在奇异之时对时空具有局部影响。
This work explains how the presence of a Type-IV singularity (a mild singularity) can influence the dynamics of a bouncing universe. In particular, we examine bounce cosmology that appears with a Type-IV singularity in the context of a ghost free Gauss-Bonnet theory of gravity. Depending on the time of occurrence of the Type-IV singularity, three different cases may arise -- when the singularity occurs before the bounce or after the bounce or at the instant of the bounce respectively. However in all of these cases, we find that in the case when the singularity "globally" affects the spacetime, the scalar power spectrum becomes red tilted and the tensor-to-scalar ratio is too large to be consistent with the observational data. Based on these findings, we investigate a different bouncing scenario which also appears with a Type-IV singularity, and the singularity affects the spacetime "locally" around the time when it occurs. As a result, and unlike to the previous scenario, the perturbation modes in the second bouncing scenario are likely to generate far away from the bounce in the deep contracting phase. This finally results to the simultaneous compatibility of the observable quantities with the Planck data, and ensures the viability of the bounce model where the Type-IV singularity has local effects on the spacetime around the time of the singularity.
