  The gravitational collapse in fourth order theories of gravity defined by an
arbitrary action of the scalar curvature shows significant deviations with
General Relativity. The presence of a new scalar mode produces a higher initial
contraction that favors the reduction of the collapsing time. However,
depending on the particular model, there are fundamental differences when the
modifications to the General Relativity collapse leave the linear regime. These
analyses can be used to exclude an important region of the parameter space
associated with alternative gravitational models.
