Exploring Signatures of New Physics in Cosmology
[eng] Cosmology is the study of the origin and evolution of our Universe as a whole. Even if the theoretical framework of Cosmology was developed a century ago, with the formulation of General Relativity by Albert Einstein, it was only during the last decades that we have seen an improvement in expe...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2020 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/151799 |
| Acceso en línea: | https://hdl.handle.net/2445/151799 http://hdl.handle.net/10803/668752 |
| Access Level: | acceso abierto |
| Palabra clave: | Cosmologia Energia fosca (Astronomia) Neutrins Forats negres (Astronomia) Cosmology Dark energy (Astronomy) Neutrinos Black holes (Astronomy) |
| Sumario: | [eng] Cosmology is the study of the origin and evolution of our Universe as a whole. Even if the theoretical framework of Cosmology was developed a century ago, with the formulation of General Relativity by Albert Einstein, it was only during the last decades that we have seen an improvement in experimental capabilities so relevant to transform Cosmology from a “data-scarce” to a “data-driven” science. This thesis is divided in five parts. The first one is constituted by an introductory chapter which describes the standard model which we use today in Cosmology, the ΛCDM model. The main ingredients of this model are a theory of gravity that describes as the Universe evolves, in this case General Relativity; the different components existing in our Universe, namely photons, neutrinos, baryons, cold dark matter (CDM) and dark energy, described by a cosmological constant Λ; and a theory explaining the initial conditions of the Universe, which we assume to be Inflation. Even if we can describe many of these aspects in great detail, we still have several open problems in the three topics (theory of gravity, components of the Universe and initial conditions theory). The second part is focused on the possible degeneracy between the effects that neutrinos y modified gravity theory have on cosmological observables. In the paper “Hiding neutrino masses in modified gravity cosmology” we investigated how Horndeski theory has enough freedom to reproduce a cosmological expansion as in ΛCDM and, at the same time, to boost the growth of structures at large scales. In fact this growth could hide the effects that massive neutrinos have in the matter power spectrum. In the third part we discuss about one of the dark matter candidate, primordial black holes. In “Primordial black holes as dark matter: converting constraints from monochromatic to extended mass distributions” we show how it is possible to obtain upper limits on the abundance of primordial black holes with an extended mass distribution starting from upper limits obtained assuming a monochromatic mass distribution. We also prove that for lognormal and power-law distributions the constraints on primordial black holes abundance in the 10 solar masses window are tighter with respect to the monochromatic case. In “GW×LSS: chasing the progenitors of merging binary black holes” we explain how, correlating gravitational waves maps and galaxies maps, we can understand if the origin of the black holes that form the detected binaries is stellar or primordial. The fourth part describes how we can obtain new probes of the first fractions of seconds of our Universe. In “Measuring the energy scale of inflation using large scale structure” we show how we can measure the energy scale of inflation through the measurement of a specific primordial non-Gaussianity signal, called “graviton exchange”. In particular we show that this primordial signal is of the same order of magnitude of the three-point function at large scale, opening the possibility of a detection. In “From primordial black holes abundance to primordial curvature power spectrum (and back)” we use the primordial black holes to put constraints on the maximum amplitude of the primordial curvature power spectrum. Specifically, we developed a procedure which connects numerical simulations of primordial black holes formation to a correct cosmological interpretation of these simulations, to a calculation of the abundance of these objects using peak theory. The fifth part includes the summary of the results found and a discussion of those very results. Moreover we discuss about future perspectives and about how to extend these works in future scientific projects. |
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