Talk detail

Participant	Zaslavskii , Oleg
Institution	Kharkov V. N. Karazin National University - Svoboda Square 4 - Kharkov - - Ukraine

Session	BH3	Accepted		Order	Time
Talk	Oral abstract	Title	Acceleration of particles by black hole horizons
Co-authors
Abstract	Brief review of the effect of acceleration of particles by rotating and charged black holes to unbound energies in the centre of mass frame is suggested. Simple and general explanations of the effect are given: (i) the kinematic one based on the behaviour of relative velocity of colliding particles near the horizon, (ii) the geometric one, based on properties of particles' four-velocities with respect to a local light cone near the horizon, The principle of "kinematic censorship" is formulated that prevents to gain infinite energy in collisions. The similar effect near the inner black hole horizon is also discussed and the role of the bifurcation point is revealed.

Session	AT3	Accepted		Order	Time
Talk	Oral abstract	Title	Quasiblack holes, black holes and membrane paradigm: Entropy and other properties
Co-authors
Abstract	Quasiblack holes are objects on the threshold of forming an event horizon. We review the properties of quasiblack holes and establish their relation to the membrane paradigm. Special emphasis is put on black hole thermodynamics where we trace how the Bekenstein-Hawking entropy arises by taking the horizon limit of regular configurations with no horizon. We also discuss the extremal case and show that in this instance the entropy is model-dependent, so here the universality of the entropy fails. Among other things it depends on how the black hole horizon has formed, i.e., on its prehistory. We also derive the black hole mass formulas in the quasiblack hole approach and discuss the spacetime structure of quasiblack holes.