Dynamics of black hole formation in an exactly solvable model

We consider the process of black hole formation in particle collisions in the exactly solvable framework of (2+1)-dimensional anti-de Sitter gravity. An effective Hamiltonian describing the near horizon dynamics of a head-on collision is given. The Hamiltonian exhibits a universal structure, with the formation of a horizon at a critical distance. Based on this, we evaluate the action for the process and discuss the semiclassical amplitude for black hole formation. The derived amplitude is seen to contain no exponential suppression or enhancement. Comments on the conformal field theory description of the process are made.