View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PhilSci Archive Global Spacetime Structure∗ John Byron Manchak
[email protected] Abstract Here, we outline the basic structure of relativistic spacetime and record a number of facts. We then consider a distinction between lo- cal and global spacetime properties and provide important examples of each. We also examine two clusters of global properties and ques- tion which of them should be regarded as physically reasonable. The properties concern \singularities" and \time travel" and are therefore of some philosophical interest. 1 Introduction The study of global spacetime structure is a study of the more foundational aspects of general relativity. One steps away from the details of the theory and instead examines the qualitative features of spacetime (e.g. its topology and causal structure). We divide the following into three main sections. In the first, we outline the basic structure of relativistic spacetime and record a number of facts. In the second, we consider a distinction between local and global spacetime properties and provide important examples of each. In the third, we examine two clusters of global properties and question which of them should be re- garded as physically reasonable. The properties concern \singularities" and \time travel" and are therefore of some philosophical interest. ∗I am grateful to Bob Batterman, Erik Curiel, and David Malament for comments on a previous draft. 1 2 Relativistic Spacetime We take a (relativistic) spacetime to be a pair (M; gab). Here M is a smooth, connected, n-dimensional (n ≥ 2) manifold without boundary.