Signature of the interaction between dark energy and dark matter in
  observations
  We investigate the effect of an interaction between dark energy and dark
matter upon the dynamics of galaxy clusters. This effect is computed through
the Layser-Irvine equation, which describes how an astrophysical system reaches
virial equilibrium and was modified to include the dark interactions. Using
observational data from almost 100 purportedly relaxed galaxy clusters we put
constraints on the strength of the couplings in the dark sector. We compare our
results with those from other observations and find that a positive (in the
sense of energy flow from dark energy to dark matter) non vanishing interaction
is consistent with the data within several standard deviations.
