BLACK HOLE AS A SUPERCOLLIDER

Abstract

Recently, it was found that in the vicinity of the black hole horizon of a rotating black hole two particles can collide in such a way that the energy in their centre of mass frame becomes infinite (so-called BSW effect). I give a brief review of basic features of this effect and show that this is a generic property of rotating black holes. In addition, there exists its counterpart for radial motion of charged particles in the charged black hole background. Simple kinematic explanation is suggested that is based on observation that all massive particles fall in two classes. In the first case (by definition, "usual particles"), the velocity approaches that of light on the horizon in the locally-nonrotating frame due to special relationship between the energy and the angular momentum. In the second case, it tends to some value less than speed of light. As a result, the relative velocity also tends to the speed of light with infinitely growing Lorentz factor.