Cosmology with CMB and Large Scale Structure
type: CreativeWork
description: Cosmology has become a precision science due to a wealth of new precise data from various astronomical observations. It is therefore important, from a methodological point of view, to develop new statistical and numerical tools to study the Cosmic Microwave Background (CMB) radiation and Large Scale Structure(LSS), in order to test different models of the Universe. This is the main aim of this thesis. The standard inflationary $\Lambda$-dominated Cold Dark Matter ($\Lambda$CDM) model is based on the premise that the Universe is statistically isotropic and homogeneous. This premise needs to be rigorously tested observationally. We study the angular correlation function $C(\theta)$ of the CMB sky using the WMAP 5-year data, and find that the low-multipoles can be reconstructed from the data outside the sky cut. We apply a Bayesian analysis and find that $S_{1/2}$ statistic ($S_{1/2}=\int [C(\theta)]^{2}d\cos \theta$, used by various investigators as a measure of correlations at large angular scales) cannot exclude the predictions of the $\Lambda$CDM model. We clarify some issues concerning estimation of correlations on large angular scales and their interpretation. To test for deviation from statistical isotropy, we develop a quadratic maximum likelihood estimator which we apply to simulated Planck maps. We show that the temperature maps from Planck mission should be able to constrain the amplitude of any spherical multipole of a scale-invariant quadrupole asymmetry at the $1\%$ level ($2\sigma$). In addition, polarization maps are also precise enough to provide complimentary constraints. We also develop a method to search for the direction of asymmetry, if any, in Planck maps. B-mode polarisation of the CMB provides another important test of models of the early Universe. Different classes of models, such as single-field inflation, loop quantum cosmology and cosmic strings give speculative but testable predictions. We find that the current ground-based experiments suc…
abstract: Cosmology has become a precision science due to a wealth of new precise data from various astronomical observations. It is therefore important, from a methodological point of view, to develop new statistical and numerical tools to study the Cosmic Microwave Background (CMB) radiation and Large Scale Structure(LSS), in order to test different models of the Universe. This is the main aim of this thesis. The standard inflationary $\Lambda$-dominated Cold Dark Matter ($\Lambda$CDM) model is based on the premise that the Universe is statistically isotropic and homogeneous. This premise needs to be rigorously tested observationally. We study the angular correlation function $C(\theta)$ of the CMB sky using the WMAP 5-year data, and find that the low-multipoles can be reconstructed from the data outside the sky cut. We apply a Bayesian analysis and find that $S_{1/2}$ statistic ($S_{1/2}=\int [C(\theta)]^{2}d\cos \theta$, used by various investigators as a measure of correlations at large angular scales) cannot exclude the predictions of the $\Lambda$CDM model. We clarify some issues concerning estimation of correlations on large angular scales and their interpretation. To test for deviation from statistical isotropy, we develop a quadratic maximum likelihood estimator which we apply to simulated Planck maps. We show that the temperature maps from Planck mission should be able to constrain the amplitude of any spherical multipole of a scale-invariant quadrupole asymmetry at the $1\%$ level ($2\sigma$). In addition, polarization maps are also precise enough to provide complimentary constraints. We also develop a method to search for the direction of asymmetry, if any, in Planck maps. B-mode polarisation of the CMB provides another important test of models of the early Universe. Different classes of models, such as single-field inflation, loop quantum cosmology and cosmic strings give speculative but testable predictions. We find that the current ground-based experiments suc…
author: Ma, Yin-Zhe
language: eng
keywords: Cosmology, Cosmic microwave background, Large Scale Structure, Velocity field
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c8100628-1e7a-4387-ae35-6024e7825c53/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2011-07-12
date modified: 2026-07-22T22:24:14Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.15994