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What can be learned about dark energy evolution?
Marian Douspis1, Yves Zolnierowski2, Alain Blanchard3, Alain Riazuelo4
(22/02/2006)

We examine constraints obtained from SNIa surveys on a two parameter model of dark energy in which the equation of state $w (z) = P(z) / \rho (z)$ undergoes a transition over a period significantly shorter than the Hubble time. We find that a transition between $w \sim -0.2$ and $w \sim -1$ (the first value being somewhat arbitrary) is allowed at redshifts as low as $0.1$, despite the fact that data extend beyond $z \sim 1$. Surveys with the precision anticipated for space experiments should allow only slight improvement on this constraint, as a transition occurring at a redshift as low as $\sim 0.17$ could still remain undistinguishable from a standard cosmological constant. The addition of a prior on the matter density $\Omega_\MAT = 0.3$ only modestly improves the constraints. Even deep space experiments would still fail to identify a rapid transition at a redshift above $0.5$. These results illustrate that a Hubble diagram of distant SNIa alone will not reveal the actual nature of dark energy at a redshift above $0.2$ and that only the local dynamics of the quintessence field can be infered from a SNIa Hubble diagram. Combinations, however, seem to be very efficient: we found that the combination of present day CMB data and SNIa already excludes a transition at redshifts below $0.8$.
1 :  IAS - Institut d'astrophysique spatiale
2 :  LAPP - Laboratoire d'Annecy le Vieux de Physique des Particules
3 :  LATT - Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées
4 :  IAP - Institut d'Astrophysique de Paris
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique
Cosmology – Cosmic microwave background – Supernovae – Cosmological parameters
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