Nongeneric null vectors
This is a sequel to [ibid., 939-962 (1993) see the preceding review] by the same authors. Here they are studying the genericity condition in general relativity for null vectors at a given point \(p\) of a Lorentz manifold. They show that at \(p\) the curvature tensor must be of the form \(R(X,Y)Z = c(g(Z,X)Y - g(Z,Y)X)\) if in the space of null vectors at \(p\) there exists an open set of non-generic null-vectors. In dimension 4 they can infer this form of the curvature tensor from the existence of 11 `generically situated' null vectors which are non-generic.
scientific article; zbMATH DE number 465602