Relativistic thick discs in the Kerr de Sitter backgrounds
Abstract
Perfect fluid tori with a uniform distribution of the specific angular momentum, ell(r, θ) = const, orbiting the Kerr de Sitter black holes or naked singularities are studied. It is well known that the structure of equipotential surfaces of such marginally stable tori reflects the basic properties of any tori with a general distribution of the specific angular momentum. Closed equipotential surfaces corresponding to stationary thick discs are allowed only in the spacetimes admitting stable circular geodesics. The last closed surface crosses itself in the cusp(s) enabling the outflow of matter from the torus due to the violation of hydrostatic equilibrium. The inner cusp enables an accretion onto the central object. The influence of the repulsive cosmological constant, Λ > 0, on the equipotential surfaces lies in the existence of the outer cusp (with a stabilizing effect on the thick discs) and in the strong collimation of open equipotential surfaces along the rotational axis. Both the effects take place near a socalled static radius where the gravitational attraction is just balanced by the cosmic repulsion. The outer cusp enables excretion, i.e., the outflow of matter from the torus into the outer space. The plusfamily discs (which are always corotating in the blackhole backgrounds but can be counterrotating, even with negative energy of the fluid elements, in some nakedsingularity backgrounds) are thicker and more extended than the minusfamily ones (which are always counterrotating in all backgrounds). For corotating discs in the nakedsingularity spacetimes, the potential well between the centre of the disc and its edges at the cusps is usually much higher than in the blackhole spacetimes. If the parameters of nakedsingularity spacetimes are very close to the parameters of extreme blackhole spacetimes, the family of possible disclike configurations includes members with two isolated discs where the inner one is always a counterrotating accretion disc.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 September 2005
 DOI:
 10.1088/02649381/22/17/019
 Bibcode:
 2005CQGra..22.3623S