The effects of dark energy on the matter-gravity coupling

Dark energy perturbations are expected to modify the evolution of cosmological perturbations, producing different observational effects. We show that these effects can be encoded in a momentum, space and polarization dependent effective matter-gravity coupling. For scalar perturbations the effective gravitational coupling can be locally negative, in regions with local dark energy under-densities. For adiabatic perturbations the effective gravitational coupling for scalar perturbations can be negative for phantom dark energy, providing a possible explanation for the observed structure suppression at low redshift, consistent with other independent evidences of evolving dark energy. For gravitational waves the effective coupling can make the radiation emitted by compact binary convalescences polarization and frequency dependent.