Speaker
Description
In this talk I will give an overview of work on non-perturbative nonlinear structure formation in ΛCDM in the context of General Relativity (GR). Using a "post-Friedmann" approximation, I will show how, at leading order, the gravito-magnetic vector potential (AKA frame-dragging potential) is generated by the momentum density on nonlinear scales, and can be extracted from ILLUSTRIS Newtonian N-body simulations, as well as from N-body simulations with GRAMSES, an approximate GR code. I will then present full-GR simulations of a toy-model “cosmic web” of over-densities, voids and filaments with the Einstein Toolkit fluid code, showing how the first shell-crossing at peaks of over-densities is very well predicted by the simple "top hat" model, while in the formation of the cosmic web a role is played by gravito-magnetism, especially around filaments.
In the last part of the talk I will illustrate some work in progress, some aimed at extending the work on frame-dragging, some aimed at understanding the role of relativistic effects during collapse and past the first shall crossing and virialization.