Duggal, K. L.; Bejancu, A. Lightlike submanifolds of codimension two. (English) Zbl 0777.53020 Math. J. Toyama Univ. 15, 59-82 (1992). The authors study the differential geometry of lightlike (degenerated) submanifolds of codimension 2 of a semi-Riemannian manifold. Taking into account the degree of degeneration two classes of lightlike submanifolds are considered, half lightlike submanifolds and totally lightlike submanifolds. In each case Gauss formulae, Weingarten formulae are obtained; second fundamental forms, shape operators are defined. Some results about totally lightlike submanifolds are given, for instance Theorem 4: Any totally lightlike surface of a 4-dimensional semi- Riemannian manifold is totally geodesic. Reviewer: B.Rouxel (Quimper) Cited in 1 ReviewCited in 5 Documents MSC: 53B25 Local submanifolds 53B30 Local differential geometry of Lorentz metrics, indefinite metrics Keywords:half lightlike submanifolds; totally lightlike submanifolds; Gauss formulae; Weingarten formulae; totally geodesic PDFBibTeX XMLCite \textit{K. L. Duggal} and \textit{A. Bejancu}, Math. J. Toyama Univ. 15, 59--82 (1992; Zbl 0777.53020)