Publication : t93/154
What can we learn from the large-scale velocity field?
Bernardeau F. (CEA, DSM, SPhT (Service de Physique Théorique), F-91191 Gif-sur-Yvette, FRANCE)Abstract:Année de publication : 1993
At large-scale the velocity field has undergone only a moderate evolution and can be analyzed by the mean of perturbation theory. In particular, I considered the properties of the one-point probability distribution function of the divergence of the smoothed peculiar velocity field expressed in units of the Hubble constant, $ \theta . $ Assuming Gaussian initial fluctuations, its skewness and its kurtosis have been calculated as a function of $ \Omega , $ $ \Lambda $ and of the shape of the power spectrum. It turns out that these quantities are weakly dependent of $ \Lambda $ but exhibit a strong $ \Omega $ dependence. Their evaluation then makes possible a determination of the density of the Universe independently of any other parameters such as a bias for the galaxy distribution, a non-zero $ \Lambda . $ Moreover a joint determination of the skewness and the kurtosis allows to test the gravitational instability scenario since there is a combination of the first three moments, $$ { \left[ \left\langle \theta^ 4 \right\rangle -3 \left\langle \theta^ 2 \right\rangle^ 2 \right] \left\langle \theta^ 2 \right\rangle \over \left\langle \theta^ 3 \right\rangle^ 2} \approx 1.6\ , $$ which is independent of all cosmological parameters (this value has been obtained for a power spectrum index $ n=-1 $ and a top-hat filter). I also show that the local peculiar velocity field, whatever the precision at which it is measured, does not carry any information on the cosmological constant.
Chapitre de livre : in: Proceedings of the 9th IAP Meeting on Cosmic Velocity Fields
Maison d'édition : Editions Frontičres, Gif-sur-Yvette, 1993
Pages : pp. 285-294
Communication : in: Proceedings of the 9th IAP Meeting on Cosmic Velocity Fields : Proceedings of the 9th IAP Meeting on Cosmic Velocity Fields ; Paris, France ; 1993-07-12 / 1993-07-17
Numéro Exterieur : CITA/93/45
Langue : Anglais
Editeurs : Bouchet F.R., Lachièze-Rey M.
