We are glad to invite you to the next Rome Joint Astrophysics Colloquium (JAC) on Friday the 15th of December at 11:30 CET.

Join in person in Aula Seminari "Grassano" of the Science Macroarea at Tor Vergata University or online with the MS Teams App https://rebrand.ly/JAC-Bruni

The Rome JAC is a joint initiative of the Physics Dept. of the Tor Vergata University of Rome, INAF - Astronomical Observatory of Rome, and INAF - Institute for Space Astrophysics and Planetology. 

TITLE: Nonlinearity in relativistic cosmology of the late and early Universe

SPEAKER: Prof. Marco Bruni (University of Portsmouth) 

ABSTRACT: In the first part of this talk I will give an overview of work on nonlinear structure formation in ΛCDM in the context of General Relativity (GR). Starting from briefly presenting a post-Friedmann approximation, I will show how gravito-magnetic effects (AKA frame-dragging)  can be extracted from standard Newtonian N-body simulations, as well as from N-body simulations with GRAMSES, a 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 second part of the talk I will move on more speculative ground, illustrating the qualitative nonlinear dynamics of  universe models with two interacting dark components, some form of dark energy  and cold dark matter (CDM), showing how an initial singularity can be avoided and the Universe can instead emerge from an unstable vacuum, or bouncing  off the same vacuum in the case of positive curvature, with a late evolution dominated by CDM and, eventually,  a stable vacuum, a scenario that should be  in agreement with observations. I will end the talk illustrating possible directions for further work in relativistic cosmology.

Poster of the event is available at: https://rebrand.ly/JAC-Bruni-Poster