Dependence on the Newman–Janis complexification prescription

Determine whether using the type-I Newman–Janis construction rather than alternative complexification prescriptions changes the degree of observational degeneracy among rotating charged regular black-hole geometries.

Background

The rotating ABG and BPR metrics in the paper are generated from their static counterparts using the Newman–Janis algorithm with type-I complexification. The paper notes that such rotating constructions are not generally guaranteed to correspond to a uniquely specified matter source.

Because alternative prescriptions for complexification can produce different rotating metrics from the same static seed, it remains unresolved whether the near-degeneracy found between some regular black holes and Kerr–Newman is a physical feature or an artifact of the type-I construction.