**Publication date:** Nov 2006

**Abstract:**

Perfect fluid tori with uniform distribution of the specific angular

momentum orbiting the Kerr-de Sitter black holes or naked singularities

are studied. Closed equipotential surfaces corresponding to stationary

toroidal discs are allowed only in the spacetimes admitting stable

circular geodesics. The last closed surface crosses itself in the

cusp(s) enabling outflow(s) of matter from the torus due to the

violation of hydrostatic equilibrium. The repulsive cosmological

constant, Λ > 0, implies the existence of the outer cusp (with

a stabilizing effect on the tori because of excretion, i.e., outflow of

matter from the torus into the outer space) and the strong collimation

of open equipotential surfaces along the rotational axis. Both the

effects take place nearby so-called static radius where the

gravitational attraction is just balanced by the cosmic repulsion. The

plus-family discs (which are always corotating in the black-hole

backgrounds but can be counterrotating, even with negative energy of the

fluid elements, in some naked-singularity backgrounds) are thicker and

more extended than the minus-family ones (which are always

counterrotating in all backgrounds). If parameters of the

naked-singularity spacetimes are very close to the parameters of 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. Mass estimates for tori with

nonrelativistic adiabatic equation of state give limits on their central

mass-density, for which the approximation of test fluid is adequate.

**Authors:**

Stuchlík, Zdeněk; Slaný, Petr;