Modelling non-linear large scale structure using Lagrangian perturbation theory re-expansions

Lagrangian perturbation theory (LPT) has been widely used to model the nonlinear growth of large scale structure analytically. However, the LPT series converges only for a finite time. In recent work, the authors have examined this issue in great detail, and proposed a new algorithm (called LPT re-expansions), to extend the domain of validity of the series. This article outlines the main ideas of the algorithm, first developed for the spherical top-hat system, and later generalized to deal with inhomogeneous initial conditions arising from random fields.