Cosmology

The evolution of the growth function of matter disturbances in different cosmological scenarios

Keywords: Cosmology; Structure and Evolution of the Universe on a large scale; Observational data

Advisor: Armando Bernui

Abstract: The evolution of the growth function of matter disturbances is a new and very important cosmological observable because it can be used to discriminate different cosmological scenarios. This observable is related to the Integrated Sachs-Wolfe effect (SWI), which is a secondary anisotropy present in the Cosmic Background Radiation, originating in the temporal variation of the gravitational potential that affects photons in the path from the last scattering surface until today. In the absence of curvature, the SWI effect indicates the presence of a dark energy component as part of the Universe's content. In this project we study alternative cosmologies to the standard LCDM model, especially the modified gravity models, using observational data of the growth function in order to eliminate the existing degeneration between the models and / or explore the possibility that any of them will be able to reproduce the data of the Universe observed as well as the LCDM. Among the objectives of this project we have: - To study observational links to Modified Gravity theories. - Analyze how cosmological observables can restrict classes of Modified Gravity theories. - Investigate mathematical properties of cosmological models alternative to LCDM.

Requirements: Knowledge of the Theory of Cosmological Disorders.

Cosmographic analysis at low redshifts using cosmological observables

Keywords: Cosmology; cosmography; cosmological observables

Advisor: Armando Bernui

Abstract: In this project we study the validity of the cosmographic approximation at a time in the Universe when it is valid, z \ in [0.0.15], and its predictions for cosmological observables, such as the Hubble function and the angular diameter distance, can compared to those obtained from the standard LCDM cosmological model. We will use observational data, which was not obtained using fiducial cosmology, to test the validity limit of cosmography in the description of the observed Universe.

Requirements: Basic knowledge of Cosmography.

Gravitational lensing of non-spherically-symmetric sources

Keywords: Cosmology, large-scale structure of the Universe, gravitational lenses

Advisor: Armando Bernui

Abstract: In this project we study the phenomenon of gravitational lensing in systems where the lens does not have spherical symmetry (for example: galaxy clusters with 2 BCG). That is, we are interested in describing slowness in non-ideal situations. For this, we first disturb a system with spherical symmetry, and study the effect produced in the convergence matrix (kappa). With this matrix, we analyzed its effect in simulated cases to learn the behavior of these non-spherically-symmetrical lenses in observational data.

Requirements: Basic knowledge of gravitational lensing.

Non-gaussian analyses in the cosmic microwave background radiation

Keywords: Cosmology; cosmic microwave background radiation; data analyses

Advisor: Armando Bernui

Abstract: Measurement and analysis of Cosmic Microwave Background (CMB) radiation has offered a demanding test to constrain cosmological parameters to high accuracy. Planck satellite has provided a map of the CMB field at all angular resolutions greater than 10 arcminutes and with temperature resolution of the order of ten part in a million (ie, 10^-5). In this project, we investigate fundamental properties in the CMB radiation data. One of these features regards the statistical distribution of the CMB temperature fluctuations, expected Gaussian in the standard cosmological model. However, significant detection of Gaussian deviations, of a given type and magnitude, can reveal crucial information about processes in the primordial Universe. Planck full mission combined the CMB temperature and E-mode polarization local maps analysis, obtained the constraints on primordial local, equilateral and orthogonal Non Gaussianities. There are various bispectrum based estimators and data analysis procedures for the challenge to search for small Gaussian deviations in the precise Planck CMB maps. In this research we tend to apply modern machine learning based techniques, like DeepSphere. Moreover, the methodology learned studying CMB properties can be used to study the large scale structure of the Universe by analyzing large data sets produced by astronomical deep surveys, like the Sloan Digital Sky Survey.

Requirements: Knowledges of cosmic microwave background radiation (CMB); knowledge of CMB data analyses.