Dissertation
Effects of Inflation Constrained to Explain Dark Energy
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005436
Handle:
https://hdl.handle.net/2376/119313
Abstract
According to inflationary cosmology, the Universe underwent a period of rapid exponential expansion very early in its history. In the simplest scenario, inflation is driven by a scalar field, namely the inflaton, slowly rolling down its potential. If inflation occurred in the very early Universe, the inflaton must have decayed and transferred its energy to the other particles in the Universe through a process known as reheating. More recently, the Universe has entered a second phase of accelerated expansion, and the mysterious energy component causing this late-time accelerated expansion has been coined dark energy. Investigating dark energy's nature remains one of the main challenges of cosmology today.
This dissertation explores the viability, effects, and predictions of the string-theory-motivated K{\"a}hler Moduli Inflation I (KMII) model which can provide a possible source for today's dark energy density due to the potential's non-vanishing minimum. The model's parameter space is explored using a Markov Chain Monte Carlo (MCMC) sampling method against the measured Cosmic Microwave Background (CMB) data. The dynamics of the model's post-inflationary reheating phase are analyzed using Floquet analysis and numerical lattice simulations, with a focus on the phenomena of self- and parametric resonant effects during the inflaton oscillations.
Although the non-vanishing minimum of the KMII potential must be very precisely fine-tuned for it to match the dark energy density observed today, the model is consistent with the measured CMB data. The allowed ranges of the model parameters are estimated, which are used to predict the inflaton's mass and a high reheating temperature of the Universe, the implications of which are discussed. The Floquet analysis results display negligible narrow-band self-resonance instabilities and no parametric resonance due to coupling in the regions of interest. Finally, the lattice simulations predict stochastic gravitational wave backgrounds (SGWBs) generated due to inhomogeneities during the inflaton oscillations that would be observable today in the $10^9 \mathrm{\mhyphen} 10^{10} \! \: \mathrm{Hz}$ frequency range.
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Details
- Title
- Effects of Inflation Constrained to Explain Dark Energy
- Creators
- Islam Iqbal Khan
- Contributors
- Guy Worthey (Advisor)Michael Forbes (Committee Member)Sukanta Bose (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Physics and Astronomy
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 148
- Identifiers
- 99900592359701842
- Language
- English
- Resource Type
- Dissertation