The effects of dark energy on the matter-gravity coupling
Antonio Enea Romano
TL;DR
This work develops a general, model-independent framework in which dark energy perturbations modify cosmological perturbations through a momentum-, space-, and polarization-dependent effective gravitational coupling $G_{\rm eff}$. It shows that scalar and tensor perturbations can experience scale- and time-dependent couplings, with the possibility of locally negative $G^{\Psi}_{\rm eff}$ in dark-energy under-dense regions and a phantom-dark-energy-induced reduction of gravity at late times. The authors connect these effects to observables, including structure growth suppression at low redshift and potential frequency/polarization-dependent gravitational-wave propagation, offering a common language between perturbation theory and modified-gravity models. The framework supports a wide class of theories with a running Planck mass and an effective dark-energy stress-energy tensor, and it provides guidance for interpreting current data and testing predictions with future GW observations.
Abstract
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 an explanation for the observed structure suppression at low redshift, consistent with other independent evidences of evolving dark energy.