Gravitational instabilities and faster evolving density perturbations - art. no. 084014

The evolution of inhomogeneities in a spherical collapse modal is studied b y expanding the Einstein equation in powers of the inverse radial parameter . In the linear regime, the density contrasjt is obtained for flat, closed, and open universes. In addition to the usual modes, an infinite number of new growing modes are contained in the solutions for pressureless open and closed universes. In the nonlinear regime, we obtain the leading growing mo des in closed forms for a flat universe and also, in the Limits of small an d large times, for an open universe. [S0556-2821(99)01408-3].