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;