Current and future supernova constraints on decaying $Λ$ cosmologies

Abstract

We investigate observational constraints from present and future supernova data on a large class of decaying vacuum cosmologies. In such scenarios the present value of the vacuum energy density is quantified by a positive $β$ parameter smaller than unity. By assuming a Gaussian prior on the matter density parameter ($Ω_{\rm{m}} = 0.35 \pm 0.07$) we find $Ω_{\rm{m}} = 0.34^{+0.14}_{-0.12}$ and $β= 0.62^{+0.12}_{-0.24}$ (95% c.l.) as the best fit values for the present data. We show that, while the current data cannot provide restrictive constraints on the $Ω_{\rm{m}} - β$ plane, the future SNe data will limit considerably the allowed space of parameter. A brief discussion about the equivalence between dynamical-$Λ$ scenarios and scalar field cosmologies is also included.