Análise do Efeito de Lentes Gravitacionais Fracas na Radiação Cósmica de Fundo

Abstract

Observations of temperature and polarization of the cosmic microwave background (CMB) provide important information of the early universe. The CMB temperature fluctuations are related to the perturbations from inflationary epoch and their statistical properties can discriminate between different classes of inflationary models. However, there are also secondary processes and the production of temperature fluctuations, generated after the last scattering surface, which can mask the primordial signal of the CMB, hence hiding the study of their intrinsic properties. One of these processes is called weak gravitational lensing effect (WL), caused by small deflections of the propagation of the photons due to inhomogeneous gravitational fields. The WL effect change the properties of RCF, since it induces distortions in the spatial pattern of CMB anisotropies. Consequently, the polarization is changed as well as the power spectrum and also their statistical properties. Moreover WL may can be used to constrain cosmological properties, since it is directly related to the large-scale structure. This thesis presents analyses of the properties of the WL effect on CMB, particularly, the study of how this effect induces non gaussian signals and changes slightly the power spectrum at small scales. These analyses consist on comparisons, using chi-square, between properties of simulated CMB maps sets, containing only primordial information and CMB with and without WL effect. The CMB maps with WL effect were produced from the lensing potential data released by the Planck satellite team. The methodology was applied in different patches on the sky, in order to look for regions of the celestial sphere that are differentially influenced by WL. Statistical analysis were based on the calculation, in each patch, of the Minkowski functional (MF) area, perimeter and genus. Moreover, the power spectrum of the maps were calculated in CMB maps with and without the WL effect, also in different patches of the sky . Our results show that there are regions of the celestial sphere in which the MF indicated comparatively larger and smaller gaussianity deviations, yet the statistical significance is low. Among the functionals, the area (perimeter) was less (high) sensitive to the type NG induced by WL. About the difference of angular power spectra, we found regions with minor and major changes due to WL however, the statistical significance remains low.