Affiliation:
1. Midnapore College (Autonomous), Vidyasagar University, India
Abstract
The notions of different types of compactness in a spacetime manifold has reviewed in this article. Also, their relations with Cauchy hypersurfaces, which play very important role in globally hyperbolic spacetimes has been discussed. For example, A be a closed subset of a spacetime M having a compact intersection with all the Cauchy hypersurfaces of it, then A⊂J(C) for some compact set C⊂M and conversely. Past and future compact sets in a spacetime and their interrelations with spacelike and timelike compactness are also discussed here by introducing necessary definitions, propositions, and diagrams wherever necessary, for the sake of understanding. Also, it is shown that, a closed advanced set is strictly future compact set. The relations among those compact sets themselves has been mentioned elaborately.