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;