Dark energy perturbations and a possible solution to the coincidence problem

We analyze some generic properties of the dark energy (DE) perturbations, in the case of a self-conserved DE fluid. We also apply a simple test (the "F-test") to compare a model to the data on large scale structure (LSS) under the assumption of negligible DE perturbations. We exemplify our discussions by means of the LXCDM model, showing that it provides a viable solution to the cosmological coincidence problem.