Reconstructing the interaction between dark energy and dark matter using
  Gaussian Processes
  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 $w=-1$, the reconstructed interaction is consistent
with the standard $\Lambda$CDM model, namely, there is no evidence for the
interaction. This also holds for the constant $w$ cases from $-0.9$ to $-1.1$
and for the Chevallier-Polarski-Linder (CPL) parametrization case. If the
equation of state deviates obviously from $-1$, 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.
