We construct an example which shows that two isocausal spacetimes, in the sense introduced recently in García-Parrado and Senovilla (2003 Class. Quantum Grav. 20 625-64), may have c-boundaries which are not equal (more precisely, not equivalent, as no bijection between the completions can preserve all the binary relations induced by causality). This example also suggests that isocausality can be useful for the understanding and computation of the c-boundary.
Classical and Quantum Gravity
- Pub Date:
- September 2011
- Mathematical Physics;
- General Relativity and Quantum Cosmology;
- Mathematics - Differential Geometry;
- Minor modifications, including the title, which matches now with the published version. 12 pages, 3 figures