Weak gravitational lensing bispectrum

Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters that govern them. The nonlinear evolution of large-scale structure produces a non-Gaussian signa l that is potentially observable in galaxy shear data. We study the three-p oint statistics of the convergence, specifically the bispectrum, using the dark matter halo approach, which describes the density field in terms of co rrelations between and within dark matter halos. Our approach allows us to study the effect of the mass distribution in observed fields, in particular the bias induced by the lack of rare massive halos (clusters) in observed fields. We show that the convergence skewness is primarily due to rare and massive dark matter halos, with skewness converging to its mean value only if halos of mass M > 10(15) M. are present. This calculational method can i n principle be used to correct for such a bias as well as to search for mor e robust statistics related to the two- and three-point correlations.