Projective structures in space-time (Q1078819)

The concept of projective equivalence in space-time is defined and it is shown that the relation of causality is preserved under projective maps. A 5-dimensional manifold analogous to the Kaluza-Klein models is defined. Causal futures of two projectively related sets are shown to be isomorphic. A result between two projectively related manifolds is established which is similar to the Schwartz lemma.