BH4 - Gravitational fields with sources: From compact objects to black holes |
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Speaker |
Patil, Mandar |
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Coauthors |
Pankaj S. Joshi, Ken-ichi Nakao, Masashi Kimura, Tomohiro Harada |
| Talk Title |
Ultra-high energy collisions around near-extremal Kerr black-holes and over-spinning Kerr geometries |
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Abstract |
In this talk we describe the process of ultra-high energy collisions between particles around near-extremal Kerr black holes and over-spinning Kerr geometry and make a critical comparison between the two. Fine-tuning of the geodesic parameters of the colliding particles is necessary to achieve large centre of mass energy in case of the black hole, while no such fine-tuning is necessary in case of the over-spinning Kerr geometry. We show that the time required for the trans-Planckian collisions of proton-like particles to occur around solar mass object is several orders of magnitude larger than the age of the universe in case of the Kerr black hole, while it is of the order of million years around over-spinning Kerr geometry. The self-gravity of the colliding particles sets an upper bound on the centre of mass energy of the colliding particles. We argue that the upper bound for the collision of proton-like particles around solar-mass object is less than Planck energy in case of the near-extremal black holes and it is much larger than Planck energy for the geometry above the extremality. We show that while most of the particles produced in the ultra-high collisions around black hole enter the event horizon, severely limiting the observability of this process, around half of the particle produced escape to infinity in case of the over-spinning geometry. |
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