Talk detail

Participant	Kimura, Masashi
Institution	Yukawa Institute for Theoretical Physics, Kyoto University - Sakyo-ku Kitashirakawa Oiwake-cho - Kyoto-shi - Kyoto - Japan

Session	BH3	Accepted	Yes	Order	9	Time	10'
Talk	Oral abstract	Title	Acceleration of colliding shells around a black hole:Validity of the test particle approximation in the BSW process
Co-authors	Ken-ichi Nakao, Hideyuki Tagoshi
Abstract	Recently, Banados, Silk and West (BSW) showed that the total energy of two colliding test particles has no upper limit in their center of mass frame in the neighborhood of an extreme Kerr black hole. The large energy of such particles would generate strong gravity, although this has not been taken into account in the BSW analysis. In this talk, in order to draw some implications concerning the effects of gravity generated by colliding particles in the BSW process, we study a collision of two spherical charged dust shells around a charged black hole. We show that the energy of two colliding shells in the center of mass frame observable from infinity has an upper limit due to their own gravity. Our result suggests that an upper limit also exists for the total energy of colliding particles in the center of mass frame in the observable domain in the BSW process due the gravity of the particles.

Session	BH1	Accepted	Yes	Order	7	Time	20'
Talk	Oral abstract	Title	Analyticity of event horizons of extremal Kaluza-Klein black holes
Co-authors	Hideki Ishihara, Ken Matsuno, Takamitsu Tatsuoka
Abstract	We discuss the analyticity of event horizons of extremal Kaluza-Klein black holes. We show that the metrics admit C^1 extension across the horizon, but some component of Riemann tensor measured by a free fall observer is always diverge at the horizon if the space time dimensions is higher than 6 unlike the case of five dimension where the event horizon is analytic. The singularity is relatively mild so that an observer along a free-fall geodesic can traverse the horizon. We also discuss the case of space times with a twisted extra dimension.