Super-Penrose process for extremal rotating neutral white holes

Abstract

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. We consider collision of two particles 1 and 2 near the horizon of the extremal rotating axially symmetric neutral generic black hole producing particles 3 and 4. We discuss the scenario in which both particles 3 and 4 fall into a black hole and move in a white hole region. If particle 1 is fine-tuned, the energy Ec.m. in the centre of mass grows unbounded (the Bañados-Silk-West effect). Then, particle 3 can, in principle, reach a flat infinity in another universe. If not only Ec.m. but also the corresponding Killing energy E is unbounded, this gives a so-called super-Penrose process (SPP). We show that the SPP is indeed possible. Thus white holes turn out to be potential sources of high energy fluxes that transfers from one universe to another. This generalizes recent observations made by Patil and Harada for the Kerr metric. We analyze two different regimes of the process on different scales.