The spherical collapse model and cluster formation beyond the $\Lambda$ cosmology: Indications for a clustered dark energy?

Understand

We generalize the small scale dynamics of the universe by taking into account models with an equation of state which evolves with time, and provide a complete formulation of the cluster virialization attempting to address the nonlinear regime of structure formation.

• In the context of the current dark energy models, we find that galaxy clusters appear to form at z\sim 1-2, in agreement with previous studies.
• Also, we investigate thoroughly the evolution of spherical matter perturbations, as the latter decouple from the background expansion and start to ``turn around'' and finally collapse.
• Within this framework, we find that the concentration parameter depends on the choice of the considered dark energy (homogeneous or clustered).