Fitting type Ia supernovae with coupled dark energy

Abstract

We discuss the possible consistency of the recently discovered type Ia supernovae atz>1 with models in which dark energy is strongly coupled to a significant fraction of darkmatter, and in which an (asymptotic) accelerated phase exists where dark matter and darkenergy scale in the same way. Such a coupling has been suggested for a possible solution ofthe coincidence problem, and is also motivated by string cosmology models of‘late time’ dilaton interactions. Our analysis shows that, for coupled dark energymodels, the recent data are still consistent with acceleration starting as early as atz = 3 (to within 90% confidence level), although at the price of a large ‘non-universality’ of thedark energy coupling to different matter fields. Also, as opposed to uncoupled models whichseem to prefer a ‘phantom’ dark energy, we find that a large amount of coupled dark matter iscompatible with present data only if the dark energy field has a conventional equation of statew>−1.