Minimal Gravitational Coupling Between Dark Matter and Dark Energy

Dark energy and dark matter are two of the biggest mysteries of modern cosmology, and our understanding of their fundamental nature is incomplete.  Many parameterizations of couplings between the two have been studied in the literature, and observational data from the growth of perturbations can constrain these parameterizations.  Dark matter and dark energy interact gravitationally over long distances, so they should at least be coupled via the graviton.  Assuming standard general relativity with no explicit coupling between dark energy and dark matter fields in the Lagrangian, we calculate the gravitational interaction cross section and examine any observational implications that may follow.