Lightlike hypersurfaces on a four-dimensional manifold endowed with a pseudoconformal structure of signature (2, 2)

Abstract

The authors study the geometry of lightlike hypersurfaces on a four-dimensional manifold $(M,c)$ endowed with a pseudoconformal structure $c=CO(2,2)$. They prove that a lightlike hypersurface $V\subset (M,c)$ bears a foliation formed by conformally invariant isotropic geodesics and two isotropic distributions tangent to these geodesics, and that these two distributions are integrable if and only if $V$ is totally umbilical. The authors also indicate how, using singular points and singular submanifolds of a lightlike hypersurface $V\subset (M,c)$, to construct an invariant normalization of $V$ intrinsically connected with $V$.

LaTeX, 23 pages