Negative Komar Masses in Regular Stationary Spacetimes

TL;DR

This paper uses a spectral method to study stationary spacetimes with black holes or dust discs surrounded by matter rings, revealing that ring-induced frame dragging can cause the Komar mass of the central object to become negative.

Contribution

It demonstrates how matter rings can drastically alter the properties of central objects, including inducing negative Komar masses, and shows a continuous transition between discs and black holes.

Findings

Matter rings can cause the Komar mass of central objects to become negative.

Frame dragging by the ring significantly affects the central object's properties.

A continuous transition exists between dust discs and black holes.

Abstract

A highly accurate multi-domain spectral method is used to study axially symmetric and stationary spacetimes containing a black hole or disc of dust surrounded by a ring of matter. It is shown that the matter ring can affect the properties of the central object drastically. In particular, by virtue of the ring's frame dragging, the so-called Komar mass of the black hole or disc can become negative. A continuous transition from such discs to such black holes can be found.