The Chronology Protection Problem in modified Kerr-Newman space-times

The paper studies causality violation via closed timelike curves (CTCs) in Kerr–Newman and in two modified Kerr–Newman geometries (a noncommutative-inspired model and an f(R) modification). It quantifies the CTC region and shows that, in both modified models, parameters can be chosen so the causality-violating region disappears. The work also discusses geodesic connectivity of the would-be CTC region and comments on causal features of Kerr–Newman–(A)dS spacetimes.

Phys. Rev. D 99, 024023 (2019)