  The degenerate nature of the metric on null hypersurfaces makes it difficult
to define a covariant derivative on null submanifolds. Recent approaches using
decomposition to define a covariant derivative on null hypersurfaces are
investigated, with examples demonstrating the limitations of the methods.
Motivated by Geroch's work on asymptotically flat spacetimes, conformal
transformations are used to construct a covariant derivative on null
hypersurfaces, and a condition on the Ricci tensor is given to determine when
this construction can be used. Several examples are given, including the
construction of a covariant derivative operator for the class of spherically
symmetric hypersurfaces.
