Novel (Non-)Accelerating Vacuum Spacetimes from Bertotti--Robinson Black Holes via Harrison and Inversion Symmetries

Abstract: We construct new vacuum solutions of the Einstein equations generated from electrovacuum configurations embedded in external electromagnetic backgrounds. Starting from accelerating Bertotti--Robinson black holes, we employ two independent mechanisms: a Melvin--Bonnor-type magnetization and an Inversion symmetry of the Einstein--Maxwell system. In both cases the external electromagnetic field can be removed, while a non-trivial gravitational backreaction remains in the metric, yielding new accelerating vacuum spacetimes of Petrov type I. In the static, non-accelerating limit, the magnetized Schwarzschild case reproduces previously known results, whereas the Inversion symmetry leads to a genuinely new vacuum configuration. These findings provide a method for generating algebraically general vacuum geometries and illustrate how electromagnetic embeddings can produce non-trivial vacuum metrics in General Relativity. The main geometrical properties of these spacetimes are discussed. Two additional results are presented in the appendices: a stationary generalization of these vacuum geometries, and two further static vacuum configurations obtained through the same symmetries but using the Alekseev--García black hole as the seed.