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Deviation from Standard Inflationary Cosmology and the Problems in Ekpyrosis


Tseng, Chien-Yao (2013) Deviation from Standard Inflationary Cosmology and the Problems in Ekpyrosis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KAHC-PK38.


There are two competing models of our universe right now. One is Big Bang with inflation cosmology. The other is the cyclic model with ekpyrotic phase in each cycle. This paper is divided into two main parts according to these two models. In the first part, we quantify the potentially observable effects of a small violation of translational invariance during inflation, as characterized by the presence of a preferred point, line, or plane. We explore the imprint such a violation would leave on the cosmic microwave background anisotropy, and provide explicit formulas for the expected amplitudes ⟨almal'm'*⟩ of the spherical-harmonic coefficients. We then provide a model and study the two-point correlation of a massless scalar (the inflaton) when the stress tensor contains the energy density from an infinitely long straight cosmic string in addition to a cosmological constant. Finally, we discuss if inflation can reconcile with the Liouville's theorem as far as the fine-tuning problem is concerned. In the second part, we find several problems in the cyclic/ekpyrotic cosmology. First of all, quantum to classical transition would not happen during an ekpyrotic phase even for superhorizon modes, and therefore the fluctuations cannot be interpreted as classical. This implies the prediction of scale-free power spectrum in ekpyrotic/cyclic universe model requires more inspection. Secondly, we find that the usual mechanism to solve fine-tuning problems is not compatible with eternal universe which contains infinitely many cycles in both direction of time. Therefore, all fine-tuning problems including the flatness problem still asks for an explanation in any generic cyclic models.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:inflation, ekpyrosis, ekpyrotic phase
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Carroll, Sean M.
Thesis Committee:
  • Wise, Mark B. (chair)
  • Carroll, Sean M. (co-chair)
  • Golwala, Sunil
  • Hirata, Christopher M.
Defense Date:21 March 2013
Record Number:CaltechTHESIS:03212013-213920050
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7547
Deposited By: Chien-Yao Tseng
Deposited On:09 Apr 2013 23:40
Last Modified:26 Oct 2021 17:37

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