In one minute

Freivogel, Kontou and Krommydas note that the classic singularity theorems of general relativity rest on energy conditions that semiclassical gravity can violate. They motivate the smeared null energy condition, a bound on the weighted average of null energy along a finite stretch of a null geodesic. Its field theory version addresses the Fewster-Roman counterexample and reduces to the averaged null energy condition over long segments. Using it as an assumption, they prove a singularity theorem that extends Penrose's theorem to semiclassical gravity. Applied to evaporating black holes and the Maldacena-Milekhin-Popov traversable wormhole, the bound is not saturated by the wormhole in four dimensions, though a reduced two-dimensional version is.

The Return of the Singularities: Applications of the Smeared Null Energy Condition