Orateur
Description
The gravitational collapse of collisionless matter produces shell-crossing singularities, beyond which standard perturbation theory breaks down. We present the fully perturbative treatment of the early post-collapse dynamics in three dimensions using Lagrangian coordinates. High-order Lagrangian perturbation theory is used up to the first shell crossing, while the generic pancake-like structure of the initial caustic allows the subsequent gravitational backreaction to be described using well-understood one-dimensional results. This leads to a post-collapse perturbation theory (PCPT) that asymptotically captures the nonlinear evolution after collapse. Comparisons with high-resolution Vlasov-Poisson simulations show that PCPTdescribes the early stages of post-shell-crossing dynamics.