  In a series of papers Amati, Ciafaloni and Veneziano and 't Hooft conjectured
that black holes occur in the collision of two light particles at planckian
energies. In this paper we discuss a possible scenario for such a process by
using the Chandrasekhar-Ferrari-Xanthopoulos duality between the Kerr black
hole solution and colliding plane gravitational waves. We clarify issues
arising in the definition of transition amplitude from a quantum state
containing only usual matter without black holes to a state containing black
holes. Collision of two plane gravitational waves producing a space-time region
which is locally isometric to an interior of black hole solution is considered.
The phase of the transition amplitude from plane waves to white and black hole
is calculated by using the Fabbrichesi, Pettorino, Veneziano and Vilkovisky
approach. An alternative extension beyond the horizon in which the space-time
again splits into two separating gravitational waves is also discussed. Such a
process is interpreted as the scattering of plane gravitational waves through
creation of virtual black and white holes.
