High Energy Particle Collisions in Superspinning Kerr Geometry
  We investigate here the particle acceleration and high energy collision in the Kerr geometry containing a naked singularity. We show that the center of mass energy of collision between two particles, dropped in from a finite but arbitrarily large distance along the axis of symmetry is arbitrarily large, provided the deviation of the angular momentum parameter from the mass is very small for the Kerr naked singularity. The collisions considered here are between particles, one of them ingoing and the other one being initially ingoing but which later emerges as an outgoing particle, after it suffers a reflection from a spatial region which has a repulsive gravity in the vicinity of the naked singularity. High energy collisions take place around a region which marks a transition between the attractive and repulsive regimes of gravity. We make a critical comparison between our results and the BSW acceleration mechanism [M. Banados, J. Silk, and S. M. West, Phys. Rev. Lett. 103, 111102 (2009).] for extremal Kerr blackholes, and argue that the scenario we give here has certain distinct advantages. If compact objects exist in nature with exterior Kerr superspinning geometry then such high energy collisions would have a significant impact on the physical processes occurring in its surrounding and could possibly lead to their own observational signatures. As an aside we also suggest a curious Gedanken collider physics experiment which could in principle be constructed in this geometry. 
Mandar Patil and Pankaj S. Joshi
gr-qc astro-ph.HE hep-ex hep-ph hep-th