I’ve been reading some interesting papers showing that stable causality holds on a spacetime assuming that causality + some other condition holds. This is some really interesting stuff.
Causality conditions on spacetimes describe how nicely behaved physics is. Causality is the condition that there are no closed causal curves. That is, no travelling back in time to the same location even if you travel at the speed of light. Stable causality says that even if the speed of light increased you couldn’t form closed causal curves, that is go back in time.
Anyway Stable Causality is also interesting as it implies the existence of a, non-unique, global time. Which is quite a powerful implication.
Go to my CiteULike page and search for Stable Causality for the papers, check the notes before you read.