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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeJan 4th 2018

at S-matrix and elsewhere is reference to the “causal order“-relation, the relation saying that for a pair $(S_1,S_2)$ of subsets of a spacetime, $S_1$ does not intersect the past of $S_2$, or equivalently that $S_2$ does not intersect the future of $S_1$.

(Following a suggestion by Arnold Neumaier, a neat suggestive notation for this is $S_1 {\vee\!\!\!\wedge} S_2$, which I have been implementing now at S-matrix.)

I am starting to give this concept its own entry, currently titled “causal order”; but what’s good terminology?

This relation ${\vee\!\!\!\wedge}$ is not really an ordering, since it is not transitive. It would seem tempting to say “causal relation”, but googling for this term shows that has an different established meaning.