Kerr–Newman Bertotti–Robinson limit

Determine the Reissner–Nordström–Bertotti–Robinson limit of the Kerr–Newman solutions embedded in the Bertotti–Robinson electromagnetic field proposed in the coordinate systems of Kerr–Bertotti and genuine Kerr–Bertotti.

Background

The paper notes that incorporating angular momentum would naturally lead to a Kerr–Newman black hole embedded in the combined Bertotti–Robinson–Bonnor–Melvin electromagnetic field. Existing Kerr–Bertotti constructions could serve as seeds for this extension, but their limiting behavior is not fully established.

In particular, the reduction of these rotating solutions to the Reissner–Nordström–Bertotti–Robinson configuration remains unresolved. Establishing this limit would provide a coordinate system and seed solution with clearly defined reductions to the relevant nonrotating and charged subcases.

References

Of course the natural generalisations could include the angular momentum to the model to get Kerr-Newman embedded in the Bertotti-Robinson-Bonnor-Melvin electromagnetic field in these spherical coordinates. It could be done in a straightforward way using, as a seed, the metric proposed in the convenient coordinate system of or . However since these solutions do not possess all the limits to their subcases clearly defined, for instance the limit to the Reissner-Nordstrom-Bertotti-Robinson remains unclear, it would be better to have the spacetime described by the coordinate system of this article.

— Reissner-Nordstrom in the Bertotti-Robinson-Bonnor-Melvin electromagnetic field  (2609.00882 - Astorino, 1 Sep 2026) in Section 4, Conclusions