A submanifold Mrn of
pseudo-Euclidean space Es4 is said to have harmonic mean curvature vector if
ΔH=0, where H denotes the mean curvature vector field and Δ the Laplacian of
the induced pseudo-Riemannian metric. We prove that every nondegenerate
Lorentz hypersurface M13 of E14 with harmonic mean curvature vector is
minimal.