  The phenomena of collapse and dispersal for a massless scalar field has drawn
considerable interest in recent years, mainly from a numerical perspective. We
give here a sufficient condition for the dispersal to take place for a scalar
field that initially begins with a collapse. It is shown that the change of the
gradient of the scalar field from a timelike to a spacelike vector must be
necessarily accompanied by the dispersal of the scalar field. This result holds
independently of any symmetries of the spacetime. We demonstrate the result
explicitly by means of an example, which is the scalar field solution given by
Roberts. The implications of the result are discussed.
