发表机构
Princeton University（普林斯顿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究具有半无限慢收缩阶段的宇宙学模型，其通过稳定吸引子、非奇异反弹解决相关问题，避免因果视界问题，产生量子涨落初始谱，规避特定定理且过去测地完备，与收缩德西特空间形成对比。
AI 中文摘要
我们表明，具有半无限慢收缩（ekpyrosis）阶段的宇宙学模型具有一系列性质，可解决宇宙学中的几个基本问题，这些问题在收缩的德西特阶段或标准大爆炸膨胀中会出现。特别是，慢收缩允许一个稳定的过去吸引子渐近于闵可夫斯基空间，以及一个稳定、平坦、均匀且各向同性的未来吸引子，其外尔曲率可忽略不计（因此引力熵也可忽略不计）。在反弹宇宙学中，这个收缩吸引子由一个平滑、非奇异的反弹终止，该反弹将收缩末期的吸引子性质转化为后续膨胀阶段的初始条件。包含慢收缩阶段的宇宙学没有粒子视界，因此避免了因果视界问题。过去的闵可夫斯基吸引子还会在所有波长上产生类似真空的量子涨落初始谱。此外，由于沿过去指向测地线的平均膨胀率非正，包含半无限慢收缩阶段的模型也规避了博德、古斯和维伦金定理，并且在过去测地线上是完备的。相比之下，收缩的德西特空间具有有限的粒子视界，并且在存在标量场、物质或辐射时会变得不稳定。
英文摘要
We show that cosmological models with a semi-infinite phase of slow contraction (ekpyrosis) possess a combination of properties that can address several fundamental problems in cosmology, otherwise faced in contracting de Sitter phases or standard big bang expansion. In particular, slow contraction admits a stable past attractor asymptoting to Minkowski space, as well as a stable, flat, homogeneous, and isotropic future attractor with negligible Weyl curvature (and, therefore, negligible gravitational entropy). In bouncing cosmologies, this contracting attractor is terminated by a smooth, non-singular bounce that transforms the attractor properties at the end of contraction into the initial conditions for the subsequent expanding phase. Cosmologies incorporating a slow contraction phase have no particle horizon and therefore avoid the causal horizon problem. The past Minkowski attractor also generates an initial spectrum of vacuum-like quantum fluctuations on all wavelengths. Moreover, because the averaged expansion rate along past-directed geodesics is non-positive, models incorporating a semi-infinite phase of slow contraction also evade the Borde,Guth and Vilenkin theorem and are past geodesically complete. By contrast, contracting de Sitter space possesses a finite particle horizon and becomes unstable in the presence of scalar fields, matter, or radiation.
Comments9 pages, 2 figures, 1 table, minor typo corrected, address change
