Stable circular orbits in higher-dimensional multi-black hole spacetimes

TL;DR

This paper investigates the existence of stable circular orbits in higher-dimensional multi-black hole spacetimes, revealing conditions under which such orbits can or cannot exist depending on the number of dimensions and black hole separation.

Contribution

It demonstrates that stable circular orbits can exist in 5D Majumdar-Papapetrou spacetimes with large black hole separation, unlike in other higher dimensions.

Findings

Stable circular orbits exist in 5D MP spacetimes with large separation.

No stable orbits in 5D MP spacetimes with small or medium separation.

Stable orbits do not exist in higher than 5D MP spacetimes for any separation.

Abstract

We consider the dynamics of particles, particularly focusing on circular orbits in the higher-dimensional Majumdar-Papapetrou (MP) spacetimes with two equal mass black holes. It is widely known that in the 5D Schwarzschild-Tangherlini and Myers-Perry backgrounds, there are no stable circular orbits. In contrast, we show that in the 5D MP background, stable circular orbits can always exist when the separation of two black holes is large enough. More precisely, for a large separation, stable circular orbits exist from the vicinity of horizons to infinity; for a medium one, they appear only in a certain finite region bounded by the innermost stable circular orbit and the outermost stable circular orbit outside the horizons; for a small one, they do not appear at all. Moreover, we show that in MP spacetimes in more than 5D, they do not exist for any separations.