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Astronomy and Astrophysics 488 (2008) 47-53
What can be learned about dark energy evolution?
M. Douspis1, Y. Zolnierowski2, A. Blanchard3, A. Riazuelo4
(09/2008)

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) / ρ (z) undergoes a transition over a period significantly shorter than the Hubble time. We find that a transition between w ˜ -0.2 and w ˜ -1 (the first value being somewhat arbitrary) is allowed at redshifts as low as 0.1, despite the fact that data extend beyond z ˜ 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 ~0.17 could still remain undistinguishable from a standard cosmological constant. The addition of a prior on the matter density Ω_m= 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 inferred 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 Astrophysique de Toulouse-Tarbes
4 :  IAP - Institut d'Astrophysique de Paris
Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique
cosmology: cosmic microwave background – cosmology: cosmological parameters – cosmology: observations