Publication date: Dec 2005
Abstract:
Perfect fluid tori with uniform distribution of the specific angular momentum, l(r θ)= const, orbiting the Kerr-de Sitter naked singularities are discussed. 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 outflows of matter from the torus due to the violation of hydrostatic equilibrium. The inner cusp enables the accretion onto the ring singularity. Influence of the repulsive cosmological constant, Λ > 0, resides in the existence of the outer cusp enabling the excretion (outflow of matter from the torus into the outer space) and gives rise to completely new type of a disc called the excretion disc. The plus-family accretion and excretion discs can be both the corotating or counterrotating discs, the minus-family ones are always the counterrotating discs, as related to locally non-rotating frames. If the parameters of naked-singularity spacetimes are very close to the parameters of the extreme black-hole spacetimes, the family of possible disc-like configurations includes members with two isolated discs where the inner one is always a counterrotating accretion disc, while the outer one can be the corotating or counterrotating excretion disc, as well as the counterrotating accretion disc.
Authors:
Slaný, Petr; Stuchlík, Zdeněk;