Le 28 février 2014
De 10h30 à 12h00
Jean-Philippe BRUNETON
LUTH, Observatoire de Paris
Standard cosmology is based on the Cosmological Principle which states that the Universe is homogeneous and isotropic. In order to go beyond that approximation, one shall take into account inhomogeneities of the matter distribution which may be relevant especially at late times. The questions here are twofold:
– To what extent do inhomogeneities influence the dynamics of the Universe ( »strong backreaction »)?
– To what extent do inhomogeneities influence the cosmological observables ( »weak backreaction »)?
These are challenging issues. In this talk we will provide a brief introduction to standard general relativity, homogeneous and inhomogeneous cosmology, and finally we shall briefly present a new (approximate) solution to Einstein field equations describing a cubic lattice of spherical masses. Such a solution can be used to represent adequately a lattice of galactic-size objects separated by inter-galactic distances. We provide a quantitative criterion for the »amount of inhomogeneity » that potentially leads to a large »weak backreaction », and further comment on the solution.