Testing General Relativity with the next generation of cosmological surveys

dc.contributor.advisorLarena, Julien
dc.contributor.advisorClarkson, Christopher
dc.contributor.authorMoloi, Teboho Abram
dc.date.accessioned2019-08-01T14:04:04Z
dc.date.available2019-08-01T14:04:04Z
dc.date.issued2019
dc.date.updated2019-07-29T13:37:02Z
dc.description.abstractThe late-time acceleration expansion of the Universe is conceptually considered the great burdensome issue in theoretical physics (cosmological problem) dubbed dark energy (DE) problem. In general relativity (GR) framework view point, there are two ways to explain where this acceleration might originate from; this riddle might either emerge from some unknown dark energy models or general relativity is a mistake on cosmological scale and dark energy is insubstantial. Innovative efforts have been carried out to comprehend the origin of the cosmic acceleration, involving surveys such as baryon acoustic oscillations (BAOs), Type Ia supernovae, weak gravitational lensing and the abundance of galaxy clusters. The next generation of cosmological surveys including LSST, DES, eBOSS, DESI, PFS, SKA and WFIRST; are aimed to provide percent-level or higher measurement of history of expansion and growth of structure over a volume which is sizable fraction of the whole observable Universe, these measurements provides strong constrains on DE. In this analysis, we investigate the Horndeski scalar-tensor theories and beyond which has been recently described in the generilized dark energy (DE) or scalar-tensor paradigm - dubbed unified dark energy (UDE). This applies the 3+1 Arnowitt-DeserMisner (ADM) formalism where a general action in unitary gauge depends on the lapse function and geometrical scalar quantities. This approach is convenient since it generates a unified framework of modified theories based on UDE or effective field theory (EFT) of linear cosmological perturbations on Friedmann-Lemaitre-Robertson-Walker (FLRW) background, this are generally characterized by five free time-dependent functions αi (αB,αH,αK,αM,αT ) each describing different properties of unified dark energy physical outcome. The evolution equations for the given UDE which assimilates beyond-Horndeski paradigms appear to correspond to a non-conservative DE scenario, in which the total energy-momentum tensor is not conserved. Furthermore, we evaluate the large-scale imprint of this UDE, by probing the two-point correlation function or power spectrum of galaxy number counts and the magnification of galaxies, on horizon scales; making sure to include the full relativistic corrections in the observed overdensity and convergence. This yield new observables which gives independent insights regarding the peculiar velocity of galaxies, the growth of structure of the Universe etc.
dc.identifier.apacitationMoloi, T. A. (2019). <i>Testing General Relativity with the next generation of cosmological surveys</i>. (). ,Faculty of Science ,Department of Maths & Applied Maths. Retrieved from http://hdl.handle.net/11427/30417en_ZA
dc.identifier.chicagocitationMoloi, Teboho Abram. <i>"Testing General Relativity with the next generation of cosmological surveys."</i> ., ,Faculty of Science ,Department of Maths & Applied Maths, 2019. http://hdl.handle.net/11427/30417en_ZA
dc.identifier.citationMoloi, T.A. 2019. Testing General Relativity with the next generation of cosmological surveys. . ,Faculty of Science ,Department of Maths & Applied Maths. http://hdl.handle.net/11427/30417en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Moloi, Teboho Abram AB - The late-time acceleration expansion of the Universe is conceptually considered the great burdensome issue in theoretical physics (cosmological problem) dubbed dark energy (DE) problem. In general relativity (GR) framework view point, there are two ways to explain where this acceleration might originate from; this riddle might either emerge from some unknown dark energy models or general relativity is a mistake on cosmological scale and dark energy is insubstantial. Innovative efforts have been carried out to comprehend the origin of the cosmic acceleration, involving surveys such as baryon acoustic oscillations (BAOs), Type Ia supernovae, weak gravitational lensing and the abundance of galaxy clusters. The next generation of cosmological surveys including LSST, DES, eBOSS, DESI, PFS, SKA and WFIRST; are aimed to provide percent-level or higher measurement of history of expansion and growth of structure over a volume which is sizable fraction of the whole observable Universe, these measurements provides strong constrains on DE. In this analysis, we investigate the Horndeski scalar-tensor theories and beyond which has been recently described in the generilized dark energy (DE) or scalar-tensor paradigm - dubbed unified dark energy (UDE). This applies the 3+1 Arnowitt-DeserMisner (ADM) formalism where a general action in unitary gauge depends on the lapse function and geometrical scalar quantities. This approach is convenient since it generates a unified framework of modified theories based on UDE or effective field theory (EFT) of linear cosmological perturbations on Friedmann-Lemaitre-Robertson-Walker (FLRW) background, this are generally characterized by five free time-dependent functions αi (αB,αH,αK,αM,αT ) each describing different properties of unified dark energy physical outcome. The evolution equations for the given UDE which assimilates beyond-Horndeski paradigms appear to correspond to a non-conservative DE scenario, in which the total energy-momentum tensor is not conserved. Furthermore, we evaluate the large-scale imprint of this UDE, by probing the two-point correlation function or power spectrum of galaxy number counts and the magnification of galaxies, on horizon scales; making sure to include the full relativistic corrections in the observed overdensity and convergence. This yield new observables which gives independent insights regarding the peculiar velocity of galaxies, the growth of structure of the Universe etc. DA - 2019 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PY - 2019 T1 - Testing General Relativity with the next generation of cosmological surveys TI - Testing General Relativity with the next generation of cosmological surveys UR - http://hdl.handle.net/11427/30417 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/30417
dc.identifier.vancouvercitationMoloi TA. Testing General Relativity with the next generation of cosmological surveys. []. ,Faculty of Science ,Department of Maths & Applied Maths, 2019 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/30417en_ZA
dc.language.rfc3066Eng
dc.publisher.departmentDepartment of Mathematics and Applied Mathematics
dc.publisher.facultyFaculty of Science
dc.titleTesting General Relativity with the next generation of cosmological surveys
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhD
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