Astrophysical black holes as particle colliders

Thomas Sotiriou, Ted Jacobson

It has recently been shown that particles falling freely from rest at infinity outside an extremal Kerr black hole can in principle collide with arbitrarily high center of mass energy. The mechanism behind this exciting result will be analyzed and particular attention will be paid in understanding the role of the maximal black hole spin assumption. A number of practical limitations will be discussed, which seem to prohibit ultra-energetic collisions near black holes in nature.