Some numerical investigations in cosmology

Simple item page
dc.contributor.advisorWeltman, Amandaen_ZA
dc.contributor.advisorHellaby, Charlesen_ZA
dc.contributor.authorWalters, Anthonyen_ZA
dc.date.accessioned2018-02-07T09:04:32Z
dc.date.available2018-02-07T09:04:32Z
dc.date.issued2017en_ZA
dc.description.abstractNumerical simulations have become an indispensable tool for understanding the complex non-linear behavior of many physical systems. Here we present two numerical investigations in cosmology. The first is posed in the context of inhomogeneous solutions to General Relativity. We lay out formalism for calculating observables in an arbitrary spacetime, for an arbitrary placed observer. In particular, we calculate the area distance, redshift and transverse motion across the observers sky. We apply our method to the Szekeres metric, and develop code in MATLAB to implement it. We successfully demonstrate that the code works for the FLRW and LT special cases, and then investigate some Szekeres models with no spherical symmetry. The second project is posed in the context of chameleon gravity. Recently, it was argued that the conformal coupling of the chameleon to matter fields created an issue for early universe cosmology. As standard model degrees of freedom become non-relativistic in the early universe, the chameleon is attracted towards a "surfing" solution, so that it arrives at the potential minimum with too large a velocity. This leads to rapid variations in the chameleon's mass and excitation of high energy modes, casting doubts on the classical treatment at Big Bang Nucleosynthesis. We propose the DBI chameleon, a consistent high energy modification of the chameleon theory that dynamically renders it weakly coupled to matter during the early universe thereby avoiding the breakdown of calculability. We demonstrate this explicitly with numerical simulations.en_ZA
dc.identifier.apacitationWalters, A. (2017). <i>Some numerical investigations in cosmology</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics. Retrieved from http://hdl.handle.net/11427/27364en_ZA
dc.identifier.chicagocitationWalters, Anthony. <i>"Some numerical investigations in cosmology."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics, 2017. http://hdl.handle.net/11427/27364en_ZA
dc.identifier.citationWalters, A. 2017. Some numerical investigations in cosmology. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Walters, Anthony AB - Numerical simulations have become an indispensable tool for understanding the complex non-linear behavior of many physical systems. Here we present two numerical investigations in cosmology. The first is posed in the context of inhomogeneous solutions to General Relativity. We lay out formalism for calculating observables in an arbitrary spacetime, for an arbitrary placed observer. In particular, we calculate the area distance, redshift and transverse motion across the observers sky. We apply our method to the Szekeres metric, and develop code in MATLAB to implement it. We successfully demonstrate that the code works for the FLRW and LT special cases, and then investigate some Szekeres models with no spherical symmetry. The second project is posed in the context of chameleon gravity. Recently, it was argued that the conformal coupling of the chameleon to matter fields created an issue for early universe cosmology. As standard model degrees of freedom become non-relativistic in the early universe, the chameleon is attracted towards a "surfing" solution, so that it arrives at the potential minimum with too large a velocity. This leads to rapid variations in the chameleon's mass and excitation of high energy modes, casting doubts on the classical treatment at Big Bang Nucleosynthesis. We propose the DBI chameleon, a consistent high energy modification of the chameleon theory that dynamically renders it weakly coupled to matter during the early universe thereby avoiding the breakdown of calculability. We demonstrate this explicitly with numerical simulations. DA - 2017 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2017 T1 - Some numerical investigations in cosmology TI - Some numerical investigations in cosmology UR - http://hdl.handle.net/11427/27364 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/27364
dc.identifier.vancouvercitationWalters A. Some numerical investigations in cosmology. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics, 2017 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/27364en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Mathematics and Applied Mathematicsen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherApplied Mathematicsen_ZA
dc.subject.otherCosmologyen_ZA
dc.titleSome numerical investigations in cosmologyen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
thesis_sci_2017_walters_anthony.pdf
Size:
14.08 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
PhD / Doctoral