Conditions for the naked singularity formation in generalized Vaidya spacetime

The gravitational collapse of generalised Vaidya spacetime is considered. It is known that the endstate of gravitational collapse, as to whether a black hole or a naked singularity is formed, depends on the mass function M ( v , r ). Here we give conditions for the mass function which corresponds to the equation of the state P = αρ where α ∈ (0, ⅓] and according to these conditions we obtain either a black hole or a naked singularity at the endstate of gravitational collapse. Also we give conditions for the mass function when the singularity is gravitationally strong. Also we provide the metric which is the analogue of Vaidya metric in case of rotation. (paper)