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A study of relativistic fluids with applications to cosmology: A variational approach
This thesis examines relativistic fluids. We have used the variational approach to develop tools for studying the dynamics of relativistic fluids to apply this to cosmological modelling. Studies like these go beyond the standard model in cosmology. Researchers believe that such extensions to the sta...
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| Format: | Thesis |
| Language: | English |
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Department of Mathematics and Applied Mathematics
2022
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| _version_ | 1867614259215597568 |
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| access_status_str | Open Access |
| author | Oreta, Timothy |
| author2 | Osano, Bob |
| author_browse | Oreta, Timothy Osano, Bob |
| author_facet | Osano, Bob Oreta, Timothy |
| author_sort | Oreta, Timothy |
| collection | Thesis |
| description | This thesis examines relativistic fluids. We have used the variational approach to develop tools for studying the dynamics of relativistic fluids to apply this to cosmological modelling. Studies like these go beyond the standard model in cosmology. Researchers believe that such extensions to the standard cosmological model are pivotal to resolving some of the long-standing cosmological problems. An example of such problems is the origin, growth (from quantum electromagnetic fluctuations to large-scale magnetic fields during inflation) and evolution of cosmological magnetic fields that exhibit as large-scale (cosmological) magnetic fields in late time. One other example is the coincidence problem. The standard approach in such studies is to use modelling in the form of the single-fluid formalism. As an alternative one can consider the single-fluid and multi-fluid formalisms that incorporate aspects of electrodynamics and thermodynamics, respectively in the context of the variational approach. This might help us make progress in trying to either resolve some of these problems or at least open up new ways of addressing them. In this regard, we have extended the well-known M¨ueller-Israel-Stewart (hereafter MIS) formalism to allow us to examine the effect on fluid flow in which the components of the multi-species fluids interact thermodynamically. We use the extension to the MIS theory in the context of interacting species to study the growth of dark matter and dark energy, and find that either interaction or entrainment involving dark energy and dark matter suggests a mutual relative modulation of the growth behaviour of the two densities. This may aid in resolving the coincidence problem. Our examination of inflation-generated, large-scale magnetic fields reveals a super-adiabatically evolving mode from the beginning of the radiation-dominated epoch to either much later during the epoch or probably extending far into the era of matter domination which may account for late time, large-scale magnetic fields. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/36098 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:49:11.967Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| 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:11427/36098 A study of relativistic fluids with applications to cosmology: A variational approach Oreta, Timothy Osano, Bob Cosmology relativistic fluids variational approach single-fluid multi-fluid dark energy dark-matter thermodynamics interaction entrainment inflation magnetic fields. This thesis examines relativistic fluids. We have used the variational approach to develop tools for studying the dynamics of relativistic fluids to apply this to cosmological modelling. Studies like these go beyond the standard model in cosmology. Researchers believe that such extensions to the standard cosmological model are pivotal to resolving some of the long-standing cosmological problems. An example of such problems is the origin, growth (from quantum electromagnetic fluctuations to large-scale magnetic fields during inflation) and evolution of cosmological magnetic fields that exhibit as large-scale (cosmological) magnetic fields in late time. One other example is the coincidence problem. The standard approach in such studies is to use modelling in the form of the single-fluid formalism. As an alternative one can consider the single-fluid and multi-fluid formalisms that incorporate aspects of electrodynamics and thermodynamics, respectively in the context of the variational approach. This might help us make progress in trying to either resolve some of these problems or at least open up new ways of addressing them. In this regard, we have extended the well-known M¨ueller-Israel-Stewart (hereafter MIS) formalism to allow us to examine the effect on fluid flow in which the components of the multi-species fluids interact thermodynamically. We use the extension to the MIS theory in the context of interacting species to study the growth of dark matter and dark energy, and find that either interaction or entrainment involving dark energy and dark matter suggests a mutual relative modulation of the growth behaviour of the two densities. This may aid in resolving the coincidence problem. Our examination of inflation-generated, large-scale magnetic fields reveals a super-adiabatically evolving mode from the beginning of the radiation-dominated epoch to either much later during the epoch or probably extending far into the era of matter domination which may account for late time, large-scale magnetic fields. 2022-03-15T12:14:03Z 2022-03-15T12:14:03Z 2021 2022-03-14T11:04:49Z Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/36098 eng application/pdf Department of Mathematics and Applied Mathematics Faculty of Science |
| spellingShingle | Cosmology relativistic fluids variational approach single-fluid multi-fluid dark energy dark-matter thermodynamics interaction entrainment inflation magnetic fields. Oreta, Timothy A study of relativistic fluids with applications to cosmology: A variational approach |
| thesis_degree_str | Doctoral |
| title | A study of relativistic fluids with applications to cosmology: A variational approach |
| title_full | A study of relativistic fluids with applications to cosmology: A variational approach |
| title_fullStr | A study of relativistic fluids with applications to cosmology: A variational approach |
| title_full_unstemmed | A study of relativistic fluids with applications to cosmology: A variational approach |
| title_short | A study of relativistic fluids with applications to cosmology: A variational approach |
| title_sort | study of relativistic fluids with applications to cosmology a variational approach |
| topic | Cosmology relativistic fluids variational approach single-fluid multi-fluid dark energy dark-matter thermodynamics interaction entrainment inflation magnetic fields. |
| url | http://hdl.handle.net/11427/36098 |
| work_keys_str_mv | AT oretatimothy astudyofrelativisticfluidswithapplicationstocosmologyavariationalapproach AT oretatimothy studyofrelativisticfluidswithapplicationstocosmologyavariationalapproach |