Existence and nature of singularities inside black-hole horizons

Determine whether black holes described by general relativity necessarily contain spacetime singularities inside their event horizons and characterize the nature of such singularities under realistic astrophysical conditions.

Background

Black-hole interiors are central to the predictive power of general relativity and to cosmic censorship hypotheses. Although singularity theorems suggest the occurrence of singularities under broad conditions, their precise existence and physical nature inside astrophysical black holes remain subjects of debate. The authors highlight this as an explicit open question in the theoretical landscape that gravitational-wave observations indirectly inform.