On the trail of dark energy

Abstract

I present some recent results on efforts to constraint the variation of dark energy as a function of redshift. In particular I concentrate on observational determinations of the expansion history H ( z ) . I review a formalism that makes use of quantities similar to the Horizon-flow parameters in inflation and is general enough that can deal with multiscalar quintessence scenarios, exotic matter components, and higher order curvature corrections to General Relativity. I show how the shape of the dark energy potential can be recovered non parametrically using this formalism and I present approximations analogous to the ones relevant to slow-roll inflation. Since presently available data do not allow a non-parametric and exact reconstruction of the potential, I consider a general parametric description. This reconstruction can also be used in other approaches followed in the literature (e.g., the reconstruction of the redshift evolution of the dark energy equation of state w ( z ) ). Using observations of passively evolving galaxies and supernova data I derive constraints on the dark energy potential shape in the redshift range 0.1 z 1.8 . Our findings show that at the 1σ level the potential is consistent with being constant, although at the same level of confidence variations cannot be excluded with current data.