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Abstract: We study non-linear structure formation in the presence of dark energy. Theinfluence of dark energy on the growth of large-scale cosmological structuresis exerted both through its background effect on the expansion rate, andthrough its perturbations as well. In order to compute the rate of formation ofmassive objects we employ the Spherical Collapse formalism, which we generalizeto include fluids with pressure. We show that the resulting non-linearevolution equations are identical to the ones obtained in the Pseudo-Newtonianapproach to cosmological perturbations, in the regime where an equation ofstate serves to describe both the background pressure relative to density, andthe pressure perturbations relative to the density perturbations as well. Wethen consider a wide range of constant and time-dependent equations of stateincluding phantom models parametrized in a standard way, and study theirimpact on the non-linear growth of structure. The main effect is the formationof dark energy structure associated with the dark matter halo: non-phantomequations of state induce the formation of a dark energy halo, damping thegrowth of structures; phantom models, on the other hand, generate dark energyvoids, enhancing structure growth. Finally, we employ the Press-Schechterformalism to compute how dark energy affects the number of massive objects as afunction of redshift.

Autor: L. R. Abramo, R. C. Batista, L. Liberato, R. Rosenfeld


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