On Lightlike Hypersurfaces In Anti De Sitter 4-space

In this paper, we define the notions of lightlike hypersurfaces and Lorentzian distance-squared function on spacelike surface in Anti de Sitter 4-space. And we establish the relationships between singularities of Lorentzian distance-squared function and geometric invariants as applications of standard techniques of singularity theory for the Lorentzian distance-squared function.