Topological censorship

The topological censorship theorem states that general relativity does not allow an observer to probe the topology of spacetime: any topological structure collapses too quickly to allow light to traverse it. More precisely, in a globally hyperbolic, asymptotically flat spacetime satisfying the null energy condition, every causal curve from past null infinity to future null infinity is fixed-endpoint homotopic to a curve in a topologically trivial neighbourhood of infinity.

References

• John L. Friedman, Kristin Schleich, and Donald M. Witt (1993). "Topological Censorship". Phys.Rev.Lett. 71 (10): 1486–1489. arXiv:gr-qc/9305017. Bibcode:1993PhRvL..71.1486F. doi:10.1103/PhysRevLett.71.1486. PMID 10054420.