On the balance problem for two rotating and charged black holes

Understand

It is an interesting open problem whether two non-extremal rotating and electrically charged black holes can be in physical equilibrium, which might be possible due to a balance between the gravitational attraction and the spin-spin and electrical repulsions.

• Exact candidate solutions were constructed, but it is unclear whether they are physically acceptable.
• These solutions were obtained by assuming a particular behaviour on the symmetry axis.
• However, it was not known whether the assumed form of the axis data covers the general case or whether data of some other type need to be considered as well.