Bubbles of nothing in binary black holes and black rings, and viceversa

TL;DR

This paper explores how expanding bubbles of nothing naturally occur in complex black hole systems with multiple or non-spherical horizons, linking Einstein-Rosen bridges and resulting in new static equilibrium configurations.

Contribution

It introduces explicit constructions of expanding bubbles in four and five dimensions as limits of black hole binaries and rings, revealing their role in black hole horizon dynamics.

Findings

Bubbles of nothing are common in multi-horizon black hole systems.

Explicit 4D and 5D bubble solutions are constructed as horizon limits.

Black hole binaries and rings can be in static equilibrium with bubbles.

Abstract

We argue that expanding bubbles of nothing are a widespread feature of systems of black holes with multiple or non-spherical horizons, appearing as a limit of regions that are narrowly enclosed by the horizons. The bubble is a minimal cycle that links the Einstein-Rosen bridges in the system, and its expansion occurs through the familiar stretching of space in black hole interiors. We demonstrate this idea (which does not involve any Wick rotations) with explicit constructions in four and five dimensions. The geometries of expanding bubbles in these dimensions arise as a limit of, respectively, static black hole binaries and black rings. The limit is such that the separation between the two black holes, or the inner hole of the black ring, becomes very small, and the horizons of the black holes correspond to acceleration horizons of the bubbles. We also explain how a five-dimensional black hole binary gives rise to a different type of expanding bubble. We then show that bubble spacetimes can host black hole binaries and black rings in static equilibrium, with their gravitational attraction being balanced against the background spacetime expansion. Similar constructions are expected in six or more dimensions, but most of these solutions can be obtained only numerically. Finally, we argue that the Nariai solution can be regarded as containing an expanding circular bubble of nothing.