Black Saturn

TL;DR

This paper constructs an exact 4+1-dimensional vacuum solution called Black Saturn, revealing unique gravitational phenomena such as non-uniqueness of black hole solutions, frame-dragging effects, and configurations with zero total angular momentum.

Contribution

It introduces the Black Saturn solution using inverse scattering, demonstrating novel gravitational effects and non-uniqueness in higher-dimensional black hole configurations.

Findings

Black Saturn exhibits 2-fold continuous non-uniqueness for fixed mass and angular momentum.

Black ring and black hole can counter-rotate to produce zero total angular momentum.

Rotational frame-dragging occurs with a black hole of zero Komar angular momentum.

Abstract

Using the inverse scattering method we construct an exact stationary asymptotically flat 4+1-dimensional vacuum solution describing Black Saturn: a spherical black hole surrounded by a black ring. Angular momentum keeps the configuration in equilibrium. Black saturn reveals a number of interesting gravitational phenomena: (1) The balanced solution exhibits 2-fold continuous non-uniqueness for fixed mass and angular momentum; (2) Remarkably, the 4+1d Schwarzschild black hole is not unique, since the black ring and black hole of black saturn can counter-rotate to give zero total angular momentum at infinity, while maintaining balance; (3) The system cleanly demonstrates rotational frame-dragging when a black hole with vanishing Komar angular momentum is rotating as the black ring drags the surrounding spacetime. Possible generalizations include multiple rings of saturn as well as doubly spinning black saturn configurations.