Dark energy in string cosmology
Main Author: | |
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Publication Date: | 2021 |
Format: | Master thesis |
Language: | eng |
Source: | Repositório Institucional da UNESP |
Download full: | http://hdl.handle.net/11449/204870 |
Summary: | In this master thesis, three string-inspired cosmological models are compared: string (brane) gas, holographic, and chameleon cosmologies. More precisely, dark energy features are found and the cosmological constant problem is analyzed in each scenario. Their possible solutions to this problem are quite different and common ground is hard to be found. While, within string gas cosmology, dark energy traits only appear in the primordial Hagedorn phase (analogous to inflation in standard cosmology) and have hardly anything to do with the currently observed cosmological constant, both holographic and chameleon cosmologies give us interesting insights on the dominant energy density in the universe today. On one hand, within holographic cosmology, one can map the cosmological constant problem to a renormalization group (RG) flow in the dual field theory. Then, the problem can be “holographically solved”, even though the precise mechanism for the bulk solution is unknown. On the other hand, the chameleon setup encourages us to motivate a scalar potential for a modulus to create a quintessence model, hoping to explain the currently observed dark energy density. In the end, it is attempted to implement the chameleon idea in the original Kaluza-Klein theory, proposing a quintessence model from its scalar field. After fixing some problems with the initial idea, it is found that the scalar potential is still not suitable to have had relevant implications on structure formation in the universe. |
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Dark energy in string cosmologyEnergia escura em cosmologia de cordasConstante cosmológicaEnergia escura (Astronomia)HolografiaKaluza-Klein, Teorias deTeoria de cordasIn this master thesis, three string-inspired cosmological models are compared: string (brane) gas, holographic, and chameleon cosmologies. More precisely, dark energy features are found and the cosmological constant problem is analyzed in each scenario. Their possible solutions to this problem are quite different and common ground is hard to be found. While, within string gas cosmology, dark energy traits only appear in the primordial Hagedorn phase (analogous to inflation in standard cosmology) and have hardly anything to do with the currently observed cosmological constant, both holographic and chameleon cosmologies give us interesting insights on the dominant energy density in the universe today. On one hand, within holographic cosmology, one can map the cosmological constant problem to a renormalization group (RG) flow in the dual field theory. Then, the problem can be “holographically solved”, even though the precise mechanism for the bulk solution is unknown. On the other hand, the chameleon setup encourages us to motivate a scalar potential for a modulus to create a quintessence model, hoping to explain the currently observed dark energy density. In the end, it is attempted to implement the chameleon idea in the original Kaluza-Klein theory, proposing a quintessence model from its scalar field. After fixing some problems with the initial idea, it is found that the scalar potential is still not suitable to have had relevant implications on structure formation in the universe.Nessa dissertação de mestrado, três modelos cosmológicos inspirados em teoria de cordas são comparados: cosmologias de gás de cordas (branas), holográfica e camaleônica. Mais precisamente, traços de energia escura são estudados e o problema da constante cosmológica é analisado em cada cenário. As possı́veis soluções para este problema são bem distintas e caracterı́sticas em comum são difı́ceis de serem encontradas. Enquanto, na cosmologia de gás de cordas, elementos de energia escura só aparecem na fase primordial de Hagedorn (análoga à inflação na cosmologia padrão) e pouco tem a ver com a constante cosmological observada atualmente, tanto a cosmologia hologŕafica quanto a camaleônica nos trazem novas informações interessantes sobre a densidade de energia dominante no universo hoje em dia. Por um lado, na cosmologia holográfica, pode-se mapear o problema da constante cosmológica ao fluxo do grupo de renormalização na teoria de campos dual. Logo, o problema pode ser “holograficamente resolvido”, mesmo que o mecanismo para a solução seja desconhecido na teoria gravitacional. Por outro lado, a ideia do camaleão nos encoraja a motivar um potencial escalar para um módulo a fim de criar um modelo de quintessência, esperando explicar a densidade de energia escura observada atualmente. No final, tentamos implementar a ideia do escalar camaleão na teoria original de Kaluza-Klein, propondo um modelo de quintessência a partir do seu campo escalar. Após retificar problemas oriundos da ideia inicial, foi notado que o potencial do campo escalar continuou não tendo as caracterı́sticas necessárias para ter tido um papel importante na formação de estruturas do universo.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)2018/25390-0Universidade Estadual Paulista (Unesp)Nastase, Horatiu Stefan [UNESP]Universidade Estadual Paulista (Unesp)Sousa, Gabriel Lucas Andrade de2021-06-07T16:44:12Z2021-06-07T16:44:12Z2021-03-31info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttp://hdl.handle.net/11449/20487033015015001P7enginfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UNESPinstname:Universidade Estadual Paulista (UNESP)instacron:UNESP2024-03-12T14:54:10Zoai:repositorio.unesp.br:11449/204870Repositório InstitucionalPUBhttp://repositorio.unesp.br/oai/requestopendoar:29462024-08-05T23:22:08.934936Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP)false |
dc.title.none.fl_str_mv |
Dark energy in string cosmology Energia escura em cosmologia de cordas |
title |
Dark energy in string cosmology |
spellingShingle |
Dark energy in string cosmology Sousa, Gabriel Lucas Andrade de Constante cosmológica Energia escura (Astronomia) Holografia Kaluza-Klein, Teorias de Teoria de cordas |
title_short |
Dark energy in string cosmology |
title_full |
Dark energy in string cosmology |
title_fullStr |
Dark energy in string cosmology |
title_full_unstemmed |
Dark energy in string cosmology |
title_sort |
Dark energy in string cosmology |
author |
Sousa, Gabriel Lucas Andrade de |
author_facet |
Sousa, Gabriel Lucas Andrade de |
author_role |
author |
dc.contributor.none.fl_str_mv |
Nastase, Horatiu Stefan [UNESP] Universidade Estadual Paulista (Unesp) |
dc.contributor.author.fl_str_mv |
Sousa, Gabriel Lucas Andrade de |
dc.subject.por.fl_str_mv |
Constante cosmológica Energia escura (Astronomia) Holografia Kaluza-Klein, Teorias de Teoria de cordas |
topic |
Constante cosmológica Energia escura (Astronomia) Holografia Kaluza-Klein, Teorias de Teoria de cordas |
description |
In this master thesis, three string-inspired cosmological models are compared: string (brane) gas, holographic, and chameleon cosmologies. More precisely, dark energy features are found and the cosmological constant problem is analyzed in each scenario. Their possible solutions to this problem are quite different and common ground is hard to be found. While, within string gas cosmology, dark energy traits only appear in the primordial Hagedorn phase (analogous to inflation in standard cosmology) and have hardly anything to do with the currently observed cosmological constant, both holographic and chameleon cosmologies give us interesting insights on the dominant energy density in the universe today. On one hand, within holographic cosmology, one can map the cosmological constant problem to a renormalization group (RG) flow in the dual field theory. Then, the problem can be “holographically solved”, even though the precise mechanism for the bulk solution is unknown. On the other hand, the chameleon setup encourages us to motivate a scalar potential for a modulus to create a quintessence model, hoping to explain the currently observed dark energy density. In the end, it is attempted to implement the chameleon idea in the original Kaluza-Klein theory, proposing a quintessence model from its scalar field. After fixing some problems with the initial idea, it is found that the scalar potential is still not suitable to have had relevant implications on structure formation in the universe. |
publishDate |
2021 |
dc.date.none.fl_str_mv |
2021-06-07T16:44:12Z 2021-06-07T16:44:12Z 2021-03-31 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/masterThesis |
format |
masterThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/11449/204870 33015015001P7 |
url |
http://hdl.handle.net/11449/204870 |
identifier_str_mv |
33015015001P7 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Estadual Paulista (Unesp) |
publisher.none.fl_str_mv |
Universidade Estadual Paulista (Unesp) |
dc.source.none.fl_str_mv |
reponame:Repositório Institucional da UNESP instname:Universidade Estadual Paulista (UNESP) instacron:UNESP |
instname_str |
Universidade Estadual Paulista (UNESP) |
instacron_str |
UNESP |
institution |
UNESP |
reponame_str |
Repositório Institucional da UNESP |
collection |
Repositório Institucional da UNESP |
repository.name.fl_str_mv |
Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP) |
repository.mail.fl_str_mv |
|
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1808128239873294336 |