Ultra-high energy collisions of nonequatorial geodesic particles near dirty black holes

Understand

We consider collision of two geodesic particles moving around rotating stationary axially symmetric black holes.

• It is shown for arbitrary nonequatorial motion that under certain conditions the energy in their centre of mass frame can grow unbound (the so-called BSW effect).
• This generalizes the previous results for equatorial motion around dirty (surrounded by matter) black holes and nonequatorial motion around the Kerr metric.
• It turns out that the BSW effect occurs near any point of the horizon surface.