Existence of event horizons in physically relevant spacetimes

Determine whether event horizons exist in physically relevant spacetimes, particularly in scenarios where Planck-scale quantum gravity modifications near classical singularities could remove the event horizon.

Background

The paper discusses fundamental limitations of event horizons in dynamical contexts, emphasizing their teleological, global nature that requires knowledge of the entire future of spacetime. This makes event horizons impractical in numerical evolutions and conceptually problematic when global assumptions (such as the existence and completeness of future null infinity) cannot be made.

The authors note earlier arguments that quantum-gravity-induced changes in a Planck-scale neighborhood of the classical singularity could eliminate the event horizon altogether. In light of such possibilities, they explicitly highlight that it is not known whether event horizons exist in physically interesting situations, motivating the use of quasi-local horizons for black hole mechanics and thermodynamics.