Structure formation in dark matter/dark energy dominated universes

In this work we present preliminary results of an analysis on the evolution of primordial baryonic and dark matter density perturbations. A top-hat hydrodynamic code has been utilized to analyze the evolution of these primordial perturbations, from the beginning of the recombination era until the redshift when the collapse occurs. All the relevant processes are included in the calculations, which includes the effect of a dark energy in the expanding universe. In particular, we find that the perturbations with dark matter collapse at very high redshift, which could explain the existence of old galaxies at high redshift. As a general result we find that the distribution of the non-baryonic dark matter is more concentrated than the baryonic one.