Null test for interactions in the dark sector

Abstract

Since there is no known symmetry in nature that prevents a nonminimal coupling between the dark energy (DE) and cold dark matter (CDM) components, such a possibility constitutes an alternative to standard cosmology, with its theoretical and observational consequences being of great interest. In this paper, we propose a new null test on the standard evolution of the dark sector based on the time dependence of the ratio between the CDM and DE energy densities which, in the standard Λ CDM scenario, scales necessarily as a− 3 . We use the latest measurements of type Ia supernovae, cosmic chronometers and angular baryonic acoustic oscillations to reconstruct the expansion history using model-independent machine learning techniques, namely, the linear model formalism and Gaussian processes. We find that while the standard evolution is consistent with the data at 3σ level, some deviations from the Λ CDM model are found at low redshifts, which may be associated with the current tension between local and global determinations of H0.