Unbounded energies of debris from head-on particle collisions near black holes

If two particles move toward a black hole and collide near the horizon, the energy E c.m. in the centre of mass can grow unbounded. This is a so-called Bañados–Silk–West (BSW) effect. One of the problems creating obstacles to the possibility of its observation consists in that individual energy E of a fragment at infinity remains finite because of redshift. We show that in the case of head-on collision, debris may have unbounded energy E. An essential ingredient of this scenario is a particle moving away from a black hole in the near-horizon region. It can appear due to precedent collision that implies multiple scattering.

Kinematics of ultra-high energy particle collisions near black holes in the magnetic field

There are different versions of collisions of two particles near black holes with unbound energy E cm in the center of mass frame. The so-called BSW effect arises when a slow fine-tuned "critical" particle hits a rapid "usual" one. We discuss a scenario of collision in the strong magnetic field for which explanation turns out to be different. Both particles are rapid but the nonzero angle between their velocities (which are both close to c, the speed of light) results in a relative velocity close to c and, hence, big E cm .

Particle Collisions in the Lower Dimensional Rotating Black Hole Space-Time with the Cosmological Constant

We study the effect of ultrahigh energy collisions of two particles with different energies near the horizon of a2+1dimensional BTZ black hole (BSW effect). We find that the particle with the critical angular momentum could exist inside the outer horizon of the BTZ black hole regardless of the particle energy. Therefore, for the nonextremal BTZ black hole, the BSW process is possible on the inner horizon with the fine tuning of parameters which are characterized by the motion of particle, while, for the extremal BTZ black hole, the particle with the critical angular momentum could only exist on the degenerated horizon, and the BSW process could also happen there.

ACCELERATION OF PARTICLES BY QUASIBLACK HOLES

If two particles collide near the black hole horizon, the energy in their center of mass (CM) frame can grow indefinitely (the so-called Bañados, Silk and West (BSW) effect). This requires fine-tuning the parameters (the energy–momentum, angular momentum or electric charge) of one particle. We show that the CM energy can be unbound also for collisions in the spacetime of quasiblack holes (QBHs) (the objects on the threshold of forming the horizon which do not collapse). It does not require special fine-tuning of parameters and occurs when any particle inside a QBH having a finite energy collides with the particle that entered a QBH from the outside region.

BLACK HOLE AS A SUPERCOLLIDER

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.

BLACK HOLE AS A SUPERCOLLIDER

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.