  The evolution of inhomogeneities in a spherical collapse model is studied by
expanding the Einstein equation in powers of inverse radial parameter. In the
linear regime, the density contrast 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 modes in
closed forms for a flat universe and also, in the limits of small and large
times, for an open universe.
