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Some numerical investigations in cosmology
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...
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| Format: | Thesis |
| Language: | English |
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Department of Mathematics and Applied Mathematics
2018
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| _version_ | 1867614292418756608 |
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| access_status_str | Open Access |
| author | Walters, Anthony |
| author2 | Weltman, Amanda |
| author_browse | Walters, Anthony Weltman, Amanda |
| author_facet | Weltman, Amanda Walters, Anthony |
| author_sort | Walters, Anthony |
| collection | Thesis |
| description | 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. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/27364 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:49:43.633Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Department of Mathematics and Applied Mathematics |
| publisherStr | Department of Mathematics and Applied Mathematics |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/27364 Some numerical investigations in cosmology Walters, Anthony Weltman, Amanda Hellaby, Charles Applied Mathematics Cosmology 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. 2018-02-07T09:04:32Z 2018-02-07T09:04:32Z 2017 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/27364 eng application/pdf Department of Mathematics and Applied Mathematics Faculty of Science University of Cape Town |
| spellingShingle | Applied Mathematics Cosmology Walters, Anthony Some numerical investigations in cosmology |
| thesis_degree_str | Doctoral |
| title | Some numerical investigations in cosmology |
| title_full | Some numerical investigations in cosmology |
| title_fullStr | Some numerical investigations in cosmology |
| title_full_unstemmed | Some numerical investigations in cosmology |
| title_short | Some numerical investigations in cosmology |
| title_sort | some numerical investigations in cosmology |
| topic | Applied Mathematics Cosmology |
| url | http://hdl.handle.net/11427/27364 |
| work_keys_str_mv | AT waltersanthony somenumericalinvestigationsincosmology |