SÉMINAIRE DU GRECO
"Post-Newtonian cosmological modelling " |
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V.A.A. Sanghai |
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I will begin by giving a brief introduction on inhomogeneities in cosmology from a theoretical and observational perspective. Then I will talk about a specific approach we have developed to probe the effect of small-scale inhomogeneities on the large-scale expansion of the universe (often referred to as the back-reaction problem in cosmology). In this approach, we take a bottom-up approach to relativistic cosmological modelling by splitting up our universe into cells. The matter content within each cell is described by the post-Newtonian formalism. At Newtonian order, we recover the standard Friedmann-like equations. At post-Newtonian orders, we obtain a correction to the large-scale expansion of the universe. As an example, we use this framework to investigate the cosmological evolution of a large number of regularly arranged point-like masses. At post-Newtonian orders, for a late time dust dominated universe, we get corrections to the dust term and we get an additional term that takes the same form as radiation. The radiation-like term is a result of the non-linearity of Einstein’s equations, and is due to the inhomogeneity present in our model. We then include a cosmological constant, radiation and spatial curvature in our model and study its influence on this radiation-like correction. |
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lundi 5 septembre 2016 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
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