Résumé / Abstract Seminaire_GReCO

"Averaged inhomogeneous cosmologies and accelerated expansion: the morphon field"

J. Larena
Lab. Univers et Théories (LUTH), Obs. Paris-Meudon-Nancay (Meudon, France)

The effective evolution of an inhomogeneous Universe in General Relativity can be described by equations for an effective volume scale factor sourced by matter and backreaction terms coming from spatial averaging of scalar variables. The backreaction terms represent the contribution of the fluctuations in the matter and metric distributions to the effective dynamics on large scales. It has been advocated that it may account for a dark energy phenomenon, responsible for the late-time accelerated expansion of Friedmannian models, with the hope to solve the coincidence problem. After an introduction of the context of averaged cosmologies, and of the possibilities to explain dark energy in this context, I will present a correspondence between backreaction and a homogeneous scalar field, called the morphon. This new field links classical inhomogeneous cosmologies to scalar field cosmologies, allowing to reinterpret, for example quintessence scenarii by routing the physical origin of the scalar field source to inhomogeneities in the Universe. This link will be exemplified through the study of a one-parameter family of scaling solutions that allows to understand the mechanism at play in a morphed cosmology: the averaged cosmology is characterized by a weak decay (quintessence) or growth (phantom quintessence) of kinematical fluctuations, fed by ''curvature energy'' that is stored in the averaged 3-Ricci curvature.

lundi 19 mars 2007 - 11:00
Salle des séminaires Évry Schatzman,
Institut d'Astrophysique de Paris

Page web du séminaire / Seminar's webpage