Interaction between dark energy and dark matter: observational constraints from OHD, BAO, CMB and SNe Ia

Understand

In order to test if there is energy transfer between dark energy and dark matter, we investigate cosmological constraints on two forms of nontrivial interaction between the dark matter sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia.

• More precisely, we find the same tendencies for both phenomenological forms of the interaction term $Q=3\gamma H\rho$, i.e., the parameter $\gamma$ to be a small number, $|\gamma|\approx 10^{-2}$.
• However, concerning the sign of the interaction parameter, we observe that $\gamma>0$ when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling ($\gamma<0$) is preferred by observations when the interaction term is proportional to dark energy density.
• We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem.