I study the joint effect of dynamical friction, tidal torques and cosmological constant on clusters of galaxies formation. I show that within high-density environments, such as rich clusters of galaxies, both dynamical friction and tidal torques slows down the collapse of low-ν peaks producing an observable variation in the time of collapse of the perturbation and, as a consequence, a reduction...

We study the occurrence and nature of naked singularities for a dust model with non-zero cosmological constant in (n + 2)-dimensional Szekeres space-times (which possess no Killing vectors) for n ≥ 2. We find that central shell-focusing singularities may be locally naked in higher dimensions but depend sensitively on the choice of initial data. In fact, the nature of the initial density determi...

We investigate here spherically symmetric gravitational collapse in a spacetime with an arbitrary number of dimensions and with a general type I matter field, which is a broad class that includes most of the physically reasonable matter forms. We show that given the initial data for matter in terms of the initial density and pressure profiles at an initial surface t = ti from which the collapse...

The gravitational collapse of spherical, barotropic perfect fluids is analyzed here. For the first time, the final state of these systems is characterized without resorting to simplifying assumptions such as self-similarity using a new approach based on non-linear o.d.e. techniques. Formation of naked singularities is shown to occur for solutions such that the mass function is sufficiently regu...