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Nonsingular bouncing cosmology.

机译：非奇异的反弹宇宙学。

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摘要

This thesis studies the cosmological theory in which the universe transitions from a contraction phase into an expansion phase through a big bounce. Primordial fluctuations that seed structure formation in the expansion phase arise from adiabatic perturbations in the preceding contraction phase. The purpose of this study is to understand how the properties of the adiabatic perturbations are affected by the bounce. In particular, a nonsingular type of bounce is considered in which the universe ceases contraction and reverses to expansion at a finite size, fully described by known theories of classical gravity and effective field theory. Two major aspects of such a nonsingular bounce are studied -- the stability of the bounce against inhomogeneities, and the power spectrum of adiabatic perturbations after the bounce. Results show that a class of bouncing models based on ghost condensation are subject to unstable growth of curvature and anisotropy, which alters the adiabatic perturbations and disrupts the nonsingular bounce. Another class of models with a ghost field are shown to have limited instability, though the contraction phase requires fine-tuning; sufficiently small perturbations can pass through the bounce and maintain a nearly scale-invariant power spectrum, consistent with observational constraints. Incorporating features of both models and resolving their problems, an ekpyrotic nonsingular bounce is proposed to support stable contraction and bouncing phases yet produce scale-invariant perturbations. Thus the nonsingular bouncing cosmology provides a possible explanation for the early universe.
机译：本文研究了宇宙学理论，其中宇宙通过一次大弹跳从收缩阶段过渡到膨胀阶段。膨胀期种子结构形成的原始波动是由前一个收缩期的绝热扰动引起的。这项研究的目的是了解反弹对绝热扰动特性的影响。特别是，考虑了一种非奇异类型的弹跳，在这种弹跳中，宇宙会在有限的大小处停止收缩并恢复膨胀，这由已知的经典引力理论和有效场论充分描述。研究了这种非奇异弹跳的两个主要方面-弹跳对不均匀性的稳定性以及弹跳后的绝热摄动功率谱。结果表明，一类基于重影凝结的弹跳模型容易受到曲率和各向异性的不稳定增长的影响，从而改变了绝热扰动并破坏了非奇异的弹跳。另一类具有重影场的模型显示出有限的不稳定性，尽管收缩阶段需要微调。足够小的扰动可以穿过反射并保持几乎不变的功率谱，这与观测约束一致。结合这两种模型的特征并解决它们的问题，提出了一种开火的非奇异弹跳，以支持稳定的收缩和弹跳阶段，但会产生尺度不变的扰动。因此，非奇异的反弹宇宙学为早期宇宙提供了可能的解释。

著录项

  • 作者

    Xue, BingKan.;

  • 作者单位

    Princeton University.;

  • 授予单位 Princeton University.;
  • 学科 Physics General.;Physics Astronomy and Astrophysics.;Physics Astrophysics.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 166 p.
  • 总页数 166
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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