Constraints on extended quintessence from high-redshift Supernovae

Abstract

We obtain constraints on quintessence models from magnitude-redshift measurements of 176 type Ia Supernovae. The considered quintessence models are ordinary quintessence, with Ratra-Peebles and SUGRA potentials, and extended quintessence with a Ratra-Peebles potential. We compute confidence regions in the $Ω_{m0}-α$ plane and find that for SUGRA potentials it is not possible to obtain useful constraints on these parameters; for the Ratra-Peebles case, both for the extended and ordinary quintessence we find $α\mincir 0.8$, at the $1σ$ level. We also consider simulated dataset for the SNAP satellite for the same models: again, for a SUGRA potential it will not be possible to obtain constraints on $α$, while with a Ratra-Peebles potential its value will be determined with an error $\mincir 0.6$. We evaluate the inaccuracy made by approximating the time evolution of the equation of state with a linear or constant $w\diz$, instead of using its exact redshift evolution. Finally we discuss the effects of different systematic errors in the determination of quintessence parameters.