Reconstructing the interaction between dark energy and dark matter using Gaussian processes

Abstract

We present a nonparametric approach to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data. In this method, once the equation of state ($w$) of dark energy is specified, the interaction can be reconstructed as a function of redshift. For the decaying vacuum energy case with $w=\ensuremath{-}1$, the reconstructed interaction is consistent with the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, namely, there is no evidence for the interaction. This also holds for the constant $w$ cases from $\ensuremath{-}0.9$ to $\ensuremath{-}1.1$ and for the Chevallier-Polarski-Linder (CPL) parametrization case. If the equation of state deviates obviously from $\ensuremath{-}1$, the reconstructed interaction exists at 95% confidence level. This shows the degeneracy between the interaction and the equation of state of dark energy when they get constraints from the observational data.