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An exotic Universe : from dark energy to wormholes

2021-05Tese de doutoramento Acesso aberto
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datacite.subject.fosCiências Naturais::Ciências Físicaspt_PT
dc.contributor.advisorNunes, Nelson
dc.contributor.advisorBarreiro, Tiago
dc.contributor.authorBarros, Bruno Jorge Castelo Branco de
dc.date.accessioned2021-09-30T16:17:52Z
dc.date.available2021-09-30T16:17:52Z
dc.date.issued2021-05
dc.date.submitted2020-11
dc.description.abstractThis thesis deals with extensions of General Relativity and their application to Cosmology and Gravitation. The introduction and main motivations of this essay can be found on Chapter 1. The second chapter proposes a dark energy model driven by a scalar field kinetically coupled to matter. The dynamics of the system are analysed through dynamical systems techniques. The background is evolved and the solutions are meticulously studied, focusing on the influence of the coupling on the cosmological parameters. Through the Planck constraints, it is derived anupper bound on the coupling parameter. Chapter three is devoted to the analysis of a conformally coupled quintessence model in which the background expansion is set to mimic a CDM evolution. Both the background and linear perturbations are analysed. The growth of structures is tested against redshift space distortions data. The spherical collapse and cluster number counts are explored, and we shed some light on the possibility to distinguish between theoretical models with regard to two surveys. An alternative formulation of General Relativity, where gravity is mediated by nonmetricity, on a flat and torsion free spacetime is exposed on the fourth Chapter. The background dynamics are set to follow the same evolution as in the standard model of Cosmology. The linear matter perturbations are evolved and the f 8 parameter is tested against large scale observations in the late Universe. Chapter five introduces a 3-form field to the Einstein-Hilbert action in the context of gravitation. Specifically, it is found wormhole solutions where the ordinary matter fields are able to coexist throughout spacetime without violating the classical energy conditions. On such scenario, the 3-form field is responsible for holding the throat of the wormhole open. On Chapter six the gravitational Lagrangian for modified Gauss-Bonnet gravity is reconstructed, such that the Friedmann equation of a bouncing Universe is recovered.pt_PT
dc.identifier.tid101597363pt_PT
dc.identifier.urihttp://hdl.handle.net/10451/49743
dc.language.isoengpt_PT
dc.relationHISTORICAL COLOR TRADITIONS AND PIGMENTS ON MURAL PAINTING: MATERIALS AND TECHNOLOGY CHARACTERIZATION OF THE ALENTEJO URBAN HERITAGE
dc.subjectEnergia escura acopladapt_PT
dc.subjectColapso esféricopt_PT
dc.subjectBuracos de vermept_PT
dc.subjectNão-metricidadept_PT
dc.subjectCosmologias ressaltopt_PT
dc.titleAn exotic Universe : from dark energy to wormholespt_PT
dc.typedoctoral thesis
dspace.entity.typePublication
oaire.awardNumberPOCI/HEC/59555/2004
oaire.awardTitleHISTORICAL COLOR TRADITIONS AND PIGMENTS ON MURAL PAINTING: MATERIALS AND TECHNOLOGY CHARACTERIZATION OF THE ALENTEJO URBAN HERITAGE
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/POCI/POCI%2FHEC%2F59555%2F2004/PT
oaire.fundingStreamPOCI
project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.nameFundação para a Ciência e a Tecnologia
rcaap.rightsopenAccesspt_PT
rcaap.typedoctoralThesispt_PT
relation.isProjectOfPublication69b782f6-a3cd-40c3-bf25-99c2693feeb1
relation.isProjectOfPublication.latestForDiscovery69b782f6-a3cd-40c3-bf25-99c2693feeb1
thesis.degree.nameTese de doutoramento, Astronomia e Astrofísica, Universidade de Lisboa, Faculdade de Ciências, 2021pt_PT

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