Euler-Poisson-Newton approach in Cosmology

Abstract

This lecture provides us with Newtonian approaches for the interpretation of two puzzling cosmological observations that are still discussed subject : a bulk flow and a foam like structure in the distribution of galaxies. For the first one, we model the motions describing all planar distortions from Hubble flow, in addition of two classes of planar-axial distortions with or without rotation, when spatial distribution of gravitational sources is homogenous. This provides us with an alternative to models which assume the presence of gravitational structures similar to Great Attractor as origin of a bulk flow. For the second one, the model accounts for an isotropic universe constituted by a spherical void surrounded by a uniform distribution of dust. It does not correspond to the usual embedding of a void solution into a cosmological background solution, but to a global solution of fluid mechanics. The general behavior of the void expansion shows a huge initial burst, which freezes asymptotically up to match Hubble expansion. While the corrective factor to Hubble law on the shell depends weakly on cosmological constant at early stages, it enables us to disentangle significantly cosmological models around redshift z ~ 1.7. The magnification of spherical voids increases with the density parameter and with the cosmological constant. An interesting feature is that for spatially closed Friedmann models, the empty regions are swept out, what provides us with a stability criterion.Comment: 15 pages, 1 figur

Dark Energy: fiction or reality?

“…18 The anthropic problem turns out to be unfounded since the respective curves of λ and Ω intersect at an abscissa a ∼ 0.75 which does not correspond to a peculiar situation within the interval ]0, a• = 1], see e.g. [23]. Only if Λ > 0 this problem can be addressed with a formulation including the future by using the conformal time, which turns out to be bounded, and the present time does not show any peculiar value, which turns out to be located nearby the asymptotical value.…”