CosmosClub: Benjamin l'Huillier (13/09/2018)

Date: September 13th 2018

Speaker: Benjamin l'Huillier (Korea Astronomy and Space Science Institute)

Title: Cosmological structure formation in LCDM and beyond: Testing LCDM with N-body simulations and advanced statistical methods [slides]


The current concordance cosmological paradigm relies on a few assumptions: gravity is described by General Relativity, the Universe is Homogeneous and Isotropic on large scales, and a phase of inflation in the early Universe. Under these assumptions, the solution to the Einstein Equations is the Friedmann—Lemaître—Robertson—Walker (FLRW) metric, a general metric describing an expanding Universe. Observationally, the Universe seems flat, dominated by dark energy, thought to be responsible for the late-time acceleration of the Universe, and by a smooth dark matter component. Albeit reasonable, these are all assumptions. Therefore, it is important to test these assumptions in order to falsify the concordance model. 
In the first part of my talk, I will show how to probe extension to the LCDM paradigm via cosmological simulations (Modified Gravity and dark energy, primordial power spectrum): how do haloes form in modified gravity? can we use the large-scale structure to probe features in the primordial power spectrum?
I will then move on to the falsification of the concordance model via model-independent tests of the concordance model from the data at the background (FLRW metric, flatness, Lambda dark energy) and the perturbation (growth rate gamma), and obtain model-independent constraints on some key cosmological parameters.