Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy
  We show that intermediate mass black holes conjectured to be the early
precursors of supermassive black holes and surrounded by relic cold dark matter
density spikes can act as particle accelerators with collisions, in principle,
at arbitrarily high centre of mass energies in the case of Kerr black holes.
While the ejecta from such interactions will be highly redshifted, we may
anticipate the possibility of a unique probe of Planck-scale physics.
