Doutorado em Astrofísica, Cosmologia e Gravitação

URI Permanente para esta coleção

http://repositorio.ufes.br/handle/10/17489

Nível: Doutorado
Ano de início: 2016
Conceito atual na CAPES: 5
Ato normativo: Parecer 487/2018
Periodicidade de seleção: Semestral
Área(s) de concentração: Astronomia e Física
Url do curso: https://cosmologia.ufes.br/pt-br/pos-graduacao/PPGCosmo/detalhes-do-curso?id=1453

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Navegando Doutorado em Astrofísica, Cosmologia e Gravitação por Autor "Amendola, Luca"

Agora exibindo 1 - 4 de 4
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    Accelerated expansion as manifestation of gravity: when dark energy belongs to the left
    (Universidade Federal do Espírito Santo, 2020-10-23) Giani, Leonardo; Amendola, Luca; Piattella, Oliver Fabio; https://orcid.org/0000000345580574; http://lattes.cnpq.br/5707156831919279; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Velten, Hermano Endlich Schneider; https://orcid.org/0000000251557998; http://lattes.cnpq.br/0282590467459210; Silva, Saulo Carneiro de Souza; https://orcid.org/000000017098383X; http://lattes.cnpq.br/5571527465158124; Iglesias, Jorge Antonio Zanelli; Kamenchtchik, Alexandre
    In order to explain the Late-times accelerated expansion of the Universe we must appeal to some form of Dark Energy. In the standard model of cosmology, the latter is interpreted as a Cosmological Constant . However, for a number of reasons, a Cosmological Constant is not completely satisfactory. In this thesis we study Dark Energy models of geometrical nature, and thus a manifestation of the underlying gravitational theory. In the rst part of the thesis we will review the CDM model and give a brief classi cation of the landscape of alternative Dark Energy candidates based on the Love lock theorem. The second part of the thesis is instead devoted to the presentation of our main results on the topic of Dark Energy. To begin with, we will report our studies about nonlocal modi cations of gravity involving the differential operator 1R, with emphasis on a speci c model and on the common behavior shared by this and similar theories in the late stages of the evolution of the Universe. Then we introduce a novel class of modi ed gravity theories based on the anticurvature tensor A (the inverse of the Ricci tensor), and assess their capability as source of Dark Energy. Finally, we will discuss a type of drift e ects which we predicted in the contest of Strong Gravitational Lensing, which could be employed both to study the e ective equation of state of the Universe and to constrain violations of the Equivalence Principle.
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    Dark matter, modified gravity and galaxy rotation curves analyses: novel methods
    (Universidade Federal do Espírito Santo, 2023-12-18) Arboleda, Alejandro Hernandez; Amendola, Luca; Rodrigues, Davi Cabral; https://orcid.org/0000000316835443; http://lattes.cnpq.br/5465449494182034; https://orcid.org/0000000321738779; http://lattes.cnpq.br/2611380047360980; Ricaldi, Wiliam Santiago Hipolito; https://orcid.org/000000021748553X; http://lattes.cnpq.br/0293080746483402; Delmestre, Karin Menendez; Marra, Valerio; https://orcid.org/0000000277731579; http://lattes.cnpq.br/6846011112691877; Rivera, Celia Del Carmen Escamilla
    The current ΛCDM cosmological model considers dark matter to be the most abundant type of matter on the universe, encompassing approximately 26.8% of it. As its name suggests, dark matter cannot be directly observed by means of electromagnetic radiation, it only interacts through gravitational fields. Historically, the discover of dark matter was made based on the study of the internal dynamics of clusters of galaxies and galaxy rotation curves. The latter provide the most precise local determination of dark matter. Currently, they continue to be one the main ways to study dark matter not only in the context of the ΛCDM but also modified theories of gravity. Here, we focus on the study of galaxy rotation curves in the context of modified gravity theories in two different but related ways: the first is an alternative approach to test whether modified gravity theories can provide or not a good fit for galaxies without previously needing individual fits. And the second one is a more focused study on a specific modified gravity theory called Vainshtein Screening. Our goal is to both develop a fast way to test viability of modified theories of gravity with rotation curves, and then focus on a specific modified gravity theory which is so far poorly explained with rotation curve data.
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    Pushing the boundaries of modern cosmology: physics beyond the Copernican principle
    (Universidade Federal do Espírito Santo, 2022-08-16) Torres, David Francisco Camarena; Marra, Valerio; https://orcid.org/0000000277731579; http://lattes.cnpq.br/6846011112691877; https://orcid.org/0000000171650439; http://lattes.cnpq.br/2093261235489631; Piattella, Oliver Fabio; https://orcid.org/0000000345580574; http://lattes.cnpq.br/5707156831919279; Amendola, Luca; https://orcid.org/0000-0002-0835-233X; http://lattes.cnpq.br/7512327723238183; Sapone, Domenico; https://orcid.org/; http://lattes.cnpq.br/; Clarkson, Chris
    The standard paradigm of modern cosmology relies on a set of fundamental assumptions that simplify and make possible the modeling of the Universe. Among these critical hypotheses, there is the presumption that we do not occupy a special place in the Uni- verse, the so-called Copernican principle. The assumption of this principle constrains the degrees of freedom allowed by the theory, and, in particular, within the framework of the General Theory of Relativity, leads to a spatially homogeneous and isotropic space-time. Here, we present a program to observationally test the Copernican princi- ple and study the cosmological applications of inhomogeneous cosmologies. Under the assumption of a spherically inhomogeneous extension of the standard model and using the latest cosmological data, we test the Copernican principle by placing constraints on radial deviations of the spatially homogeneous and isotropic space-time. We also forecast the precision with which future surveys, such as DES, Euclid and LSST, will be able to test the Copernican principle and test their ability to detect any possible violations. Furthermore, we investigate if a local void could explain away the 5σ discrepancy between the early and late times determinations of the Hubble constant. Our goal is to take the first steps to extend the boundary of the standard paradigm of modern cosmology, and, in particular, to develop a suitable framework for the development of physics beyond the Copernican principle.
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    Testing clustering dark energy models with the skewness of matter distribution
    (Universidade Federal do Espírito Santo, 2022-10-10) Fazolo, Raquel Emy; Velten, Hermano Endlich Schneider; https://orcid.org/0000000251557998; http://lattes.cnpq.br/0282590467459210; https://orcid.org/0000000340365170; Piattella, Oliver Fabio; https://orcid.org/0000000345580574; http://lattes.cnpq.br/5707156831919279; Amendola, Luca; Marinoni, Christian; Rampf, Cornelius
    This work aims to test clustering dark energy with the cosmological skewness, the third statistical moment of the matter density distribution. Usually, dark energy is treated as a cosmological constant or a fluid with negative pressure that has the properties to accelerate the cosmic background expansion. We start our analysis by explaining the standard treatment about dark energy, then cosmological perturbations are introduced. In general relativity it is not trivial to work with higher order perturbations so we make a transition to the Neo Newtonian cosmology, using the fluid dynamics equations that are equivalent to the general relativity ones to a good approximation. We then studied the cosmological skewness in two approaches: the single-fluid and two-fluid analysis. In the first approach, we model the universe as an effective single fluid where the dark energy background contributions and perturbations are included via the total equation of state parameter. This is indeed a very simplified attempt, but this analysis was useful to provide preliminary hints about how dark energy affects the skewness of matter distribution. We then apply a more general approach, modeling the universe as two non-interacting components, pressureless matter and dark energy which is a more realistic scenario. The single fluid analysis shows a great increase in skewness when including the clustering dark energy terms. This can be explained by including the terms directly in the matter equation, not just as an additional source for the gravitational field. The two fluid model results show values around the standard cosmological ones. Tests are performed to probe the skewness dependence with the cosmological parameters. Until this work, only an expression for the skewness as a function of the matter density parameter Ωm0 was available in the literature. We go beyond introducing several fits for the cosmological skewness value as a function of the dark energy equation of state wde and the dark energy speed of sound c2 de. This result has been presented in the literature for the first time. In order to check the consistency of our results, we finish with an observational analysis using CFHTLS-Wide data. Whereas the current available data is not enough to promote the skewness to the status of a precise cosmological test, further analysis and observations are indeed needed to make skewness a better tool to study dark energy models in the future.