A note on the boundary of a static Lorentzian manifold.
The authors generalize the notion of convexity from the Euclidean signature to Lorentzian signature. To this end they use geodesics, and define a set to be convex iff with each two of its points, if they can be joined by a geodesic arc, this arc also lies within this set. They give several characterizations for convexity, and use a variational principle for the proofs.
scientific article; zbMATH DE number 1780864