When working in semi-Euclidean space, we observe that the properties associated with the contacts of a given submanifold with null cone and lightlike hyperplanes have a special relevance from the geometrical viewpoint.
In [11-13], the current authors and so forth pursued with this line by describing the invariant geometric properties of Lorentzian surfaces of codimension two in semi-Euclidean space that arise from their contacts with null cone. For this purpose, the task of this paper is to study some local properties of these Lorentzian surfaces in semi-Euclidean (n + l)-space.
In Section 4, we discuss the contact between lightlike hypersurfaces and null cone by Montalds theorem.
There exist some special submanifolds in [R.sup.n + 1.sub.2], such as unit pseudo-n-sphere [S.sup.n.sub.2], anti de Sitter n-space [H.sup.n.sub.1], null cone [[LAMBDA].sup.n.sub.1], and Lorentz torus [S.sup.1.sub.t] x [S.sup.n - 1.sub.s], which have the same definitions as in .
In this case, we call each [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] a tangent null cone of M at [p.sub.0].