| Gravitational lensing is the most direct way to probe the mass distribution in the Universe. Many effects due to weak gravitational lensing are being measured, and the perspective for future data is very promising in quantity and quality. These effects carry precious information about the large-scale structure and the geometry of the Universe, whose determination and understanding are major goals of Cosmology.; This thesis explores theoretically two effects associated to weak gravitational lensing: the QSO-galaxy association, and the cosmic shear of background galaxies. I calculate the QSO-galaxy angular correlation induced by weak gravitational lensing for several cosmological models, studying its dependence on cosmological parameters and mechanisms of structure formation. I investigate the potential of weak gravitational lensing maps obtained from cosmic shear measurements to differentiate between distinct cosmological models. Using simulations, I calculate several lensing statistics, which are used to compare cosmological models. I also study the non-Gaussian features of lensing maps, and the dependence of lensing measures on cosmological evolution. Many predictions are made, and their future confrontation with observations will lead to a considerable increase in the information about our Universe. |
