Charged and rotating multi-black holes in an external gravitational field

We construct analytical and regular solutions in four-dimensional General Relativity which represent multi-black hole systems immersed in external gravitational field configurations. The external field background is composed by an infinite multipolar expansion, which allows to regularise the conical singularities of an array of collinear static black holes. A stationary rotating generalisation is achieved by adding independent angular momenta and NUT parameters to each source of the binary configuration. Moreover, a charged extension of the binary black hole system at equilibrium is generated. Finally, we show that the binary Majumdar-Papapetrou solution is consistently recovered in the vanishing external field limit. All of these solutions reach an equilibrium state due to the external gravitational field only, avoiding in this way the presence of any string or strut defect.

Automated summary

In this paper, we study multi-black hole systems immersed in external gravitational field configurations in four-dimensional General Relativity. By using an infinite multipolar expansion, the conical singularities of a series of collinear static black holes are regularized. We also achieve a stationary rotating black hole system by adding independent angular momenta and NUT parameters to each source of the binary configuration. Furthermore, a charged extension of the binary black hole system at equilibrium is generated. Lastly, we demonstrate the consistent recovery of the binary Majumdar-Papapetrou solution in the vanishing external field limit.