SÉMINAIRE DU GRECO
"The light-cone averaging and the luminosity-redshift relation" |
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Giovanni Marozzi |
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I will show a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Afterwards, using such formalism, together with adapted "geodesic light-cone" coordinates, I will show as induced backreaction effect emerges from correlated fluctuations in the luminosity distance and covariant integration measure. Considering a realistic stochastic spectrum of inhomogeneities of primordial (inflationary) origin, we find that the induced backreaction on the luminosity-redshift relation is larger than naively expected but alone cannot account for the observed effects of dark energy at large-redshifts. A full second-order calculation, or even better a reliable estimate of contributions from the non-linear regime, appears to be necessary before firm conclusions on the correct interpretation of the data can be drawn. |
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lundi 6 février 2012 - 11:00 Salle des séminaires François Arago , Institut d'Astrophysique de Paris |
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