#
Gravitational lensing and exact geometrical models for astrophysical systems in the cosmological context

In this talk I will present the generalization of a novel formalism **[GM11]** of weak gravitational lensing in the cosmological context. It is aimed to deal with the whole curvature produced by the geometry of the lens and therefore with its complete energy-momentum tensor T_{ab} , in contrast with standard approaches that only takes into account the timelike component of T_{ab} . I also will comment about the importance of considering possible contributions of spacelike component of T_{ab} as a source for the lenses and its implication in the mass determination of some astrophysical systems. The new expressions that we obtain are very general since they are written in terms of departures from the background cosmological curvature instead of metric perturbations in terms of usual potentials **[BM16b]**. Additionally, our approach only deals with weak lensing observables instead of being based in the discussion of deviation angles and contains in a natural way the possible effect of the relative motion of the lens respect to the observer. In a second part I will present new geometrical models with spheroidal (prolate and oblate) symmetry which are intended to be useful tools to describe some features of astrophysical systems; in particular, we construct a simple model of void with spheroidal symmetry and exhibit the results of its weak lensing observables using the formalism developed **[BM16a]**.
###
References

**[BM16a]** Ezequiel F. Boero and Osvaldo M. Moreschi. Geometrical models for the study of astrophysical systems with spheroidal symmetry imbedded in a standard cosmology: The case of cosmic voids. arXiv.1611.05832, 2016.

**[BM16b]** Ezequiel F. Boero and Osvaldo M. Moreschi. Gravitational lens optical scalars in terms of energy-momentum distributions in the cosmological framework. arXiv.1610.06032, 2016.

**[GM11]** Emanuel Gallo and Osvaldo M. Moreschi. Gravitational lens optical scalars in terms of energy-momentum distributions. Phys.Rev., D83:083007, 2011.