Key points are not available for this paper at this time.
The Zel'dovich approximation is often used to mimic the effects of nonlinear gravitational time evolution. The authors compare the predictions of the Zel'dovich approximation with those of the true nonlinear time evolution, for the probability distribution of mass density fluctuations averaged over a Gaussian ball of large radius, and for the large-scale streaming velocities of objects that do not trace the mass.
Grinstein et al. (Tue,) studied this question.