The three-point correlation function in cosmology

With the advent of high-quality surveys in cosmology the full three-point correlation function will be a valuable statistic for describing structure formation models. It contains information on cosmological parameters and detailed halo properties that cannot be extracted from the two-point correlation function. We use the halo clustering model to analytically calculate the three-point correlation function (3PCF) for general cosmological fields. We present detailed results for the configuration dependence of the 3-dimensional mass and galaxy distributions and the 2-dimensional cosmic shear field. We work in real space, where higher order correlation functions on small scales are easier to measure and interpret, but halo model calculations get rapidly intractable. Hence we develop techniques that allow for the accurate evaluation of all the contributing terms to real space correlations. We apply them to the 3PCF to show how its configuration and scale dependence changes as one transits from the nonlinear to the quasilinear regime, and how this depends on the relative contributions from the 1-, 2- and 3-halo terms. The 3PCF violates the hierarchical ansatz in both its scale and configuration dependence.