On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett <bhkell...@optusnet.com.au> wrote: > > That is a semantic matter. There is a problem if one insists that > "non-local" means the propagation of a real physical influence (particle of > wave) faster-than-light. But "non-locality" in standard quantum usage means > the above -- the entangled state acts as a single physical unit even when > its components are widely separated.
I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. Bruno should be aware that in the discussion you and I had earlier, you used this sort of qualitative non-standard definition to argue even if the function giving values of physical variables at each point *does* depend solely on data from the past light cone, that is "irrelevant" to deciding whether the theory is "local" in your sense, presumably because you think there can be qualitative features of the function itself that can make it "non-local" for reasons unrelated to the question of what data the function takes as input. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.