Abstract. What is the shape of space in a spacetime? One way of addressing this issue is to consider edgeless spacelike submanifolds of the spacetime. An alternative is to foliate the spacetime by timelike curves and consider the quotient obtained by identifying points on the same timelike curve. In this paper we investigate each of these notions and obtain conditions such that it yields a meaningful shape of space. We also consider the relationship between these two notions and find conditions for the quotient space to be diffeomorphic to any edgeless spacelike hypersurface. In particular, we find conditions in which merely local behaviour (being spacelike) combined with the correct behaviour on the homotopy level guarantees that a putative shape of space really is precisely that.

PACS number: 0420

Print publication: Issue 1 (7 January 2001)
Received 13 June 2000