Perfect fluid tori orbiting Kehagias–Sfetsos naked singularities

Abstract

We construct perfect fluid tori in the field of the Kehagias–Sfetsos (K–S) naked singularities. These are spherically symmetric vacuum solutions of the modified Hořava quantum gravity, characterized by a dimensionless parameter $$\omega M^2$$ , combining the gravitational mass parameter M of the spacetime with the Hořava parameter $$\omega $$ , reflecting the role of the quantum corrections. In dependence on the value of $$\omega M^2$$ , the K–S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures, demonstrating clear distinction to the properties of the torii in the Schwarzschild spacetimes. In all of the K–S naked singularity spacetimes the tori are located above an “antigravity” sphere where matter can stay in a stable equilibrium position, which is relevant for the stability of the orbiting fluid toroidal accretion structures. The signature of the K–S naked singularity is given by the properties of marginally stable tori orbiting with the uniform distribution of the specific angular momentum of the fluid, $$l=$$ const. In the K–S naked singularity spacetimes with $$\omega M^2 > 0.2811$$ , doubled tori with the same $$l=$$ const can exist; mass transfer between the outer torus and the inner one is possible under appropriate conditions, while only outflow to the outer space is allowed in complementary conditions. In the K–S spacetimes with $$\omega M^2 < 0.2811$$ , accretion from cusped perfect fluid tori is not possible due to the non-existence of unstable circular geodesics.