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Abstract: Cosmological analysis based on currently available observations are unable torule out a sizeable coupling among the dark energy and dark matter fluids. Weexplore a variety of coupled dark matter-dark energy models, which satisfycosmic microwave background constraints, in light of low redshift and nearuniverse observations. We illustrate the phenomenology of different classes ofdark coupling models, paying particular attention in distinguishing betweeneffects that appear only on the expansion history and those that appear in thegrowth of structure. We find that while a broad class of dark coupling modelsare effectively models where general relativity GR is modified -and thus canbe probed by a combination of tests for the expansion history and the growth ofstructure-, there is a class of dark coupling models where gravity is stillGR, but the growth of perturbations is, in principle modified. While thiseffect is small in the specific models we have considered, one should bear inmind that an inconsistency between reconstructed expansion history and growthmay not uniquely indicate deviations from GR. Our low redshift constraintsarise from cosmic velocities, redshift space distortions and dark matterabundance in galaxy voids. We find that current data constrain thedimensionless coupling to be |xi|<0.2, but prospects from forthcoming data arefor a significant improvement. Future, precise measurements of the Hubbleconstant, combined with high-precision constraints on the growth of structure,could provide the key to rule out dark coupling models which survive othertests. We shall exploit as well weak equivalence principle violation arguments,which have the potential to highly disfavour a broad family of coupled models.



Author: Laura Lopez Honorez, Beth A. Reid, Olga Mena, Licia Verde, Raul Jimenez

Source: https://arxiv.org/







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