Gravitational collapse in an expanding universe: Asymptotic self-similar solutions

The collapse and virialization of self-similar spherical density perturbations to a flat Einstein-de Sitter universe is investigated and in particular the asymptotic similarity solutions. Previous calculations of Gunn and Fillmore & Goldreich of the asymptotic solutions are improved here and the collapse factor of a given spherical shell is calculated. Within the framework of the asymptotic behavior exact analytical solutions are obtained.