Doutorado em Astrofísica, Cosmologia e Gravitação
URI Permanente para esta coleção
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 Assunto "Astrofísica"
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- ItemAstrophysical tests of strong-field gravity: pulse profile modeling and boundary conditions in neutron stars(Universidade Federal do Espírito Santo, 2025-03-14) Costa, Tulio Ottoni Ferreira da; Rueda Hernández, Jorge Armando; https://orcid.org/0000-0003-4904-0014; http://lattes.cnpq.br/2748521487712356; Coelho, Jaziel Goulart; https://orcid.org/0000-0001-9386-1042; http://lattes.cnpq.br/0298932683600051; https://orcid.org/0000-0003-3785-4918; http://lattes.cnpq.br/0721147143986351; Araújo, José Carlos Neves de; https://orcid.org/0000-0003-4418-4289; http://lattes.cnpq.br/6217296674061205; Arbañil, José; https://orcid.org/0000-0002-2623-4900; http://lattes.cnpq.br/2580853999834669; Velten, Hermano Endlich Schneider; https://orcid.org/0000-0002-5155-7998; http://lattes.cnpq.br/0282590467459210We live in a golden age to explore gravity in the strong field regime of compact objects. Present and future multimessenger experiments will allow precision tests with high-energy electromagnetic radiation and gravitational waves, probing the relativistic environment of compact objects. This thesis comprises two main parts and explores the strong gravity of neutron stars (NS). In the first part, we compute bolometric light curves from emitting hot spots on the surface of pulsars in the context of the Scalar-Tensor theory of gravity. This calculation considers several relativistic ingredients that affect the observed flux, such as Doppler shift, light bending, and time delay. We show that highly compact NSs, with compactness close to GM/Rc2 ∼ 0.284, are ideal astrophysical laboratories to seek deviations of General Relativity (GR) because of the light curve’s sensitivity to the gravity theory. In the second part, we explore the possibility of non-rigid rotation of NSs, studying a toy model that captures the main idea of a stratified rotation. We show the impact of different parts of the NS rotating with different angular velocities on the moment of inertia, exploring some of its astrophysical consequences. Our study aims to call attention to possible systematics when performing inference of NS parameters by techniques such as the timing of radio pulses or pulse profile modeling when assuming that the star rotates rigidly.
- ItemProbing cosmology with an eye on Rubin : from strong lensing to the large scale structure of the universe(Universidade Federal do Espírito Santo, 2024-04-11) Oliveira, Renan Alves de; Ho, Shirley ; https://orcid.org/0000-0002-1068-160X; Makler, Martín; https://orcid.org/0000-0003-2206-2651; http://lattes.cnpq.br/6567844719949395; https://orcid.org/0000-0002-0200-3833; http://lattes.cnpq.br/1895596998416086; Abramo, Luis Raul Weber ; https://orcid.org/0000-0001-8295-7022; http://lattes.cnpq.br/4558796258762790; Bom, Clécio Roque de ; https://orcid.org/0000-0003-4383-2969; http://lattes.cnpq.br/5635352837026339; Velten, Hermano Endlich Schneider ; https://orcid.org/0000-0002-5155-7998; http://lattes.cnpq.br/0282590467459210; Marra, Valerio ; http://orcid.org/0000-0002-7773-1579; http://lattes.cnpq.br/6846011112691877In 2024, the Vera C. Rubin Observatory will begin observing the Universe for the next ten years. Two key cosmological observables that Rubin will probe are gravitational lensing and the large-scale structure of the Universe. In this thesis, we derive analytical solutions for strongly lensed images that can be useful for generating fast simulations and as a starting point in parameter searches for lens inversion. Then, we obtain an expression in closed form for the magnification cross-section, which can be used to predict the abundance of highly magnified sources. Next, we focus on real data and assemble an extensive compilation of Strong Lensing candidate systems from the literature containing over 30,000 unique objects. We cross-match this sample with the current major photometric and spectroscopic catalogs. As preparation for Rubin, we generate image cutouts for these systems in most current wide-field surveys with subarcsecond seeing, namely DES, HSC, KiDS, CFHTLens, RCSLens, and CS82. This sample dubbed the “Last Stand Before Rubin” (LaStBeRu), has a myriad of applications, from using archival data to selections for follow-up projects and training of machine learning algorithms. As an application, we have performed a test of General Relativity (GR) with these data, combining information from strong lensing and velocity dispersions, which allow one to set constraints on the Post-Newtonian parameter γPPN. From the LaStBeRu database, we were able to provide the first independent test of γPPN from previous results and for the first time only for systems identifiable in ground-based images. We can obtain the most stringent constraint on γPPN by combining these data with the current samples. Moreover, we have obtained new spectroscopic data for systems selected from LaStBeRu, which were used to obtain the first end-to-end determination of γPPN. It is also the first determination derived purely from ground-based data and the first to use self-consistent priors. Our results are consistent with GR at the ∼ 1-σ level and with the previous results from the literature. Finally, in the context of the large structure, we present two neural emulators capable of making fast predictions for the density, displacement, and velocity fields of dark matter particles without necessarily having to run expensive N-body simulations. We compared these emulators with another fast method for the same task, showing that neural emulators provide the best results