Is there some result on existence of marginally trapped surfaces in spacetime 4-manifolds?
Am I right in saying that a marginal surface (like a trapped surface in general) is a compact spacelike 2-surface by definition, so if we assume a spacelike hypersurface embedded in the manifold, does that mean that there has to be a marginal surface contained in that hypersurface, or is there some other weaker existence result?
Edit: I have considered this and obviously the answer is negative, as it would depend on the spacetime as to whether it contains a marginal surface.