In this paper, we focus on a marginally trapped submanifold f: ⁿ M^n+2₁ in a Lorentzian manifold M^n+2₁. We show that f lies in a certain null hypersurface Nf^n+1 in M^n+2₁ and f has a locally volume-maximizing property in Nf^n+1 if M^n+2₁ satisfies the null energy condition.
Riku Kishida (Tue,) studied this question.