Spherical “top-hat” collapse in general-Chaplygin-gas-dominated universes

Abstract

We expand previous works on the spherical ''top-hat'' collapse framework in generalized-Chaplygingas-dominated universes. Here we allow the collapse in all energetic components within the system. We analyze the nonlinear stages of collapse for various choices of parameter of the generalized-Chaplygingas model introducing an exact formulation for the so-called effective sound speed, c 2 eff . We show that, within the spherical top-hat collapse framework, the growth of the structure becomes faster with increasing values of .

Viscous Chaplygin gas models as spherical top-hat collapsing fluids

“…Also, the perturbed EoS remains positive at the present epoch as well as near future ( Figures 5 and 11) in both cases. It can be also remarked that some of our results are consistence with [9,10,14,19,20,21].…”

“…where θ = ∇.v is the divergence of the peculiar velocity v. The dynamical equations of density contrast δ and θ can be calculated as [14] …”

“…One assumes a spherical top hat profile for the perturbed region, i.e. a spherically symmetric perturbation in some region of space with constant density [14]. The assumption of a top hat profile leads to the SC model as the uniformity of the perturbation is maintained throughout the collapse, making its evolution only time dependent.…”

“…A fully non-linear analysis is a cumbersome task usually handled by hydrodynamical/Nbody numerical codes (see e.g. [14,16]). …”

“…Carturan and Finelli [18] conducted same investigations for GCG. Hence, Fernandes et al [14] studied the evolution of density perturbation in a universe dominated by CG. Their model gave the required density contrast observed in large scale structures of universe in Newtonian approach.…”