Given a null hypersurface L of a Lorentzian manifold, we construct a
Riemannian metric g on it from a fixed transverse vector field
ζ. We study the relationship between the ambient Lorentzian manifold, the
Riemannian manifold (L,g) and the vector field ζ. As an
application, we prove some new results on null hypersurfaces, as well as known
ones, using Riemannian techniques.Comment: 26 page