Strong gravitational lensing: Why no central black holes?

We explore the scale and angular dependence of the cosmic shear three-point correlation function. The shear field is found to have a much more complex three-point function than the convergence field, but it also exhibits specific motifs which show signatures of gravitational lensing. Exact shear patterns are inferred analytically for some geometrical shear triplets configurations, when simple interpretations can be derived. A more complete description of their geometrical properties is then carried out from ray-tracing numerical simulations and simple models. These patterns reveal typical features that can be utilized for non-Gaussian signal detection in cosmic shear surveys. We test the robustness of these properties against complex noise statistics and nontrivial survey topologies. From these conclusive checks, we predict that the VIRMOS-DESCART survey should allow a detection of a non-Gaussian signal with a comfortable significance for a low matter density Universe.