Spacetime topology is the topological structure of spacetime, a topic studied primarily in general relativity. This physical theory models gravitation as a Lorentzian manifold (a spacetime) and the concepts of topology thus become important in analysing local as well as global aspects of spacetime. The study of spacetime topology is especially important in physical cosmology.
Types of topology
There are two main types of topology for a spacetime :
Path or Zeeman topology
It is the finest topology which induces the same topology as does on timelike curves.
A base for the topology is sets of the form for some point and some convex normal neighbourhood .
( denote the chronological past and future).
The Alexandrov topology on spacetime, is the coarsest topology such that both and are open for all subsets .
This topology coincides with the manifold topology if and only if the manifold is strongly causal but in general it is coarser.
Note, that in mathematics, an Alexandrov topology on a partial order is usually taken to be the coarsest topology in which only the upper sets are required to be open. Nowadays, the correct mathematical term for the Alexandrov topology on spacetime would be the interval topology, but when Kronheimer and Penrose introduced the term this difference in nomenclature was not as clear, and in physics the term Alexandrov topology remains in use.
- E. C. Zeeman Causality Implies the Lorentz Group J. Math. Phys. April 1964 Volume 5, Issue 4, pp. 490–493
- S. W. Hawking, A. R. King, P. J. McCarthy A new topology for curved space–time which incorporates the causal, differential, and conformal structures J. Math. Phys. February 1976 Volume 17, Issue 2, pp. 174–181