Física

URI Permanente desta comunidade

http://repositorio.ufes.br/handle/10/17492
Programa de Pós-Graduação em Física

Centro: CCE
Telefone: (27) 4009 2488
URL do programa: http://www.fisica.ufes.br/pos-graduacao/PPGFis

Navegar

Navegando Física por Autor "Alcaniz, Jailson Souza de"

Agora exibindo 1 - 4 de 4
  • Nenhuma Miniatura disponível
    Item
    As supernovas tipo Ia e a cosmologia
    (Universidade Federal do Espírito Santo, 2010-08-09) Oliveira, Paulo Louzada Castro de; Fabris, Júlio César; Ricaldi, William Santiago Hipolito; Alcaniz, Jailson Souza de
    This dissertation is dedicated to the investigation on the nature of the dark matter and dark energy in the Universe through the technique that uses the observations of explosions os supernovae type Ia as indicators of distances, used at the end of the last century to detect the acelerated expansion of the Universe. Since then some projects dedicated to observation of supernovae where executed and published their results, which are used here to estimate parameters and compare cosmological models. The objective of this work is to study the power of the test based on the distances to supernovae and its response to different cosmological models and free parameters. To begin with we review the standard model of Cosmology and the evidences that suport the existance of dark matter and dark energy, followed by a study on the supernovae itself and its various observational and astrophysical aspects that allow the construction of the magnitude calibration techniques and the estimatives of its distances. Before moving on to the cosmological analyses we introduce the appropriate tool which is the bayesian statistics, studied here only in its basic tools and aplications. At last we aply these tools to the supernovae data sets available in the literature know as the Gold, SNLS, Essence and Constitution, to study some cosmological models, beginning with the concordance ?CDM model and the ?CDM parametrization that tests the supposition that ?X = -1 for the dark energy. After that we test two dynamical vaccum energy ?(t) models and a special case of the quartessence Generalized Chaplygin Gas model. The results show that when used alone the supernovae data sets leeds to quite less expressive results when compared to the literature where they are used together with other evidences. And also two of the data sets including the most up to date show unexpected irregularities that point to the existance of still uncontrolled effects on the magnitude calibration techniques. Both results show that the cosmological test based on supernovae data will go through another significant improvement on its quality in the near future.
  • Nenhuma Miniatura disponível
    Item
    Interações no Setor Escuro do Universo
    (Universidade Federal do Espírito Santo, 2012-03-09) Castro, Roly David Rodriguez; Zimdahl, Winfried Ernst Wilhelm; Alcaniz, Jailson Souza de; Fabris, Júlio César; Piatella, Oliver Fabio; Wilhelm, Zimdahl, Winfried Ernst
    Interactions between dark matter and dark energy modify the dynamics of the cosmological standard model. In particular, they may be relevant in attempts to alleviate the cosmic coincidence problem. In this dissertation we study a class of interactions that result in a power law with respect to the scale factor for the ratio of the energy densities of both dark components. We generalize this approach to include time-varying equations of state for the dark energy. We obtain analytic solutions for two special cases. We confront the theoretical results with observations from supernovas type Ia and other observational data. We perform a statistical analysis and classify models with and without interactions according to information criteria. The relevance of the interacting models for the coincidence problem is discussed.
  • Nenhuma Miniatura disponível
    Item
    Modelos e observáveis além da hipótese de homogeneidade da cosmologia padrão.
    (Universidade Federal do Espírito Santo, 2019-07-11) Isidro, Eddy Giusepe Chirinos; Marra, Valerio; https://orcid.org/0000000277731579; http://lattes.cnpq.br/6846011112691877; https://orcid.org/; http://lattes.cnpq.br/0005920198522960; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Ricaldi, Wiliam Santiago Hipolito; https://orcid.org/000000021748553X; http://lattes.cnpq.br/0293080746483402; Leo, Armando Bartolome Bernui; https://orcid.org/0000-0003-3034-0762; http://lattes.cnpq.br/6926651124954505; Alcaniz, Jailson Souza de
    In the first part of this thesis we present three works developed in the first years of my PhD. The first is based on considering an effective viscous pressure as a result of the backreaction of inhomogeneities within Buchert’s formalism. We considered an effective metric with a time-dependent radius of curvature and performed observational tests with data from Supernovae Ia and compared with other models (among them ΛCDM). In the second work, we describe, in the context of the Lemaître-Tolman-Bondi metric (LTB), two flat and inhomogeneous big bang time models. Depending on the sign of the derivative, with respect to r, of the inhomogeneous big bang time we will have a local overdensity or a local underdensity. These models are toy models, which will be fitted to supernova data. We also discuss future measurements of redshift drift as a promising tool for discriminating between inhomogeneous configurations and the standard model. In the third paper we again consider effects of cosmological backreaction within Buchert’s formalism, but this time based on an explicit solution of LTB dynamics that is linear in the curvature parameter and has an inhomogeneous big bang time. This configuration represents an exactly solvable toy model but does not adequately describe our real universe. This “inconsistency” is verified by comparing our results with supernova data and with differential age data from old galaxies (cosmic chronometers). In our last work we will describe the cosmos with modelindependent analyses. This will be possible thanks to galaxy maps that enable detailed studies on the nature of fluctuations in the density of the Universe and the formation of large scale structures. We will study the Baryon Acoustic Oscillations (BAO) scale, since it is a characteristic scale imprinted on the distribution of galaxies and cosmic background radiation (CMB), which can be used as standard rule. To find the radial BAO scale we use the recipe by E. Sánchez et al. 2013. We then perform the observational tests with data from the third phase of the Baryon Oscillation Spectroscopic Survey (BOSS) from the Sloan Digital Sky Survey (SDSS-DR12) and verified our results with simulated data from MultiDark-PATCHY DR12.
  • Nenhuma Miniatura disponível
    Item
    Perturbações da matéria num modelo cosmológico com interações no setor escuro
    (Universidade Federal do Espírito Santo, 2014-04-29) Fuño, Alonso Romero; Zimdahl, Winfried Ernst Wilhelm; Velten, Hermano Endlich Schneider; Alcaniz, Jailson Souza de; Ricaldi, Wiliam Santiago Hipolito
    Interactions in the dark sector change the cosmological standard dynamic. In particular, they can be relevant to alleviate the problem of coincidence. In this thesis we study a cosmological model in which dark matter and dark energy interact in such a way that the ratio between the densities of the energies obeys a power law with respect to the scale factor. This model was introduced in the literature to address the problem of coincidence and the dynamics of the homogeneous and isotropic background has been studied in previous works. The present work extends this model to include deviations from homogeneity in the Universe. Small perturbations of homogeneity may grow due to gravitational instability to finally form the structures that we observe today. While these inhomogeneities are small, their growth can be studied by a perturbation theory of first order. We did a study of this perturbative dynamics both at the Newtonian and the relativistic levels. On the other hand, we actualize previous studies of the background dynamics by taking into account the most recent SNIa data. Basically, the model is tested against data from type Ia supernovae samples of SDSS, Constitution and Union 2.1. Within a simplified Newtonian theory we study the influence of the coupling between matter and dark energy on the dynamics of matter perturbations. On the basis of a relativistic gauge invariant theory we calculate the power spectrum of the matter and confront the results with data from the large-scale structure of the 2dFGRS and SDSS DR7 projects. Moreover, we perform a joint analysis of the background level with the perturbative level