100 YEARS OF RELATIVITY - INTERNATIONAL CONFERENCE ON CLASSICAL AND QUANTUM ASPECTS OF GRAVITY AND COSMOLOGY

Since neither dark matter nor dark energy have been detected in laboratory experiments, one may ask whether they really are two distinct physical entities, or if the observed clustering of matter and the accelerated expansion of the universe could be produced by a single component. This last alternative has motivated the quest for models of unifying dark matter, a.k.a. `quartessence'. A few quartessence candidates were proposed and investigated in the literature. Considerable attention is being devoted to explore observational predictions that can be contrasted to the data to constrain or even discard such models. We show that a wide class of adiabatic quartessence models can be ruled out by observations of the matter distribution in large scales. However, models with a given type of intrinsic entropy perturbations are still allowed by current data. Nevertheless they might leave a clear signature in the weak lensing skewness that could be detectable with next generation experiments, such as the Dark Energy Survey. Here we report our progress in the investigation of the quartessence scenario, presenting recent results for several models. We emphasize the need to consider the nonlinear regime of structure formation to probe quartessence. In our personal view, the quest can be close to an end, with the outcome being against dark matter/energy unification.