On Tue, Dec 17, 2024 at 5:42 PM Alan Grayson <[email protected]> wrote:
> On Monday, December 16, 2024 at 11:27:46 PM UTC-7 Alan Grayson wrote: > > On Monday, December 16, 2024 at 10:20:51 PM UTC-7 Bruce Kellett wrote: > > On Tue, Dec 17, 2024 at 3:11 PM Alan Grayson <[email protected]> wrote: > > On Saturday, December 14, 2024 at 5:56:21 AM UTC-7 John Clark wrote: > > On Sat, Dec 14, 2024 at 4:13 AM Alan Grayson <[email protected]> wrote: > > *> If local realism is falsified by Bell experiments, does that mean > non-locality is affirmed?* > > > *No.* > *John K Clark See what's on my new list at Extropolis > <https://groups.google.com/g/extropolis>* > > > Is this the general consensus in the physics community, or is there none. > Is this just your opinion? AG > > > Clark is quite wrong about this. Neither realism nor determinism have > anything to do with Bell's theorem. The theorem is entirely and exclusively > about locality. This is spelled out fairly clearly in the review paper by > Brunner *at al*. (arxiv.org/abs/1303.2849) If we assume locality, Bell's > theorem states that certain inequalities must be satisfied. Quantum > mechanics violates those inequalities. Therefore, quantum mechanics, in any > interpretation, is non-local. > > The proof is fairly straightforward. Informally, locality means that if we > have two disjoint points, A and B, separated by some distance , either > spacelike or timelike, then what happens at point A cannot affect what > happens at point B, and what happens at point B cannot affect what happens > at point A. This informal notion can be formalized by saying that the joint > probability for outcomes a at point A , and b at point B, must factorize, > so that the joint probability can be written as a product of two terms, one > dependent only on factors local to point A, and the other dependent only on > factors local to point B: > > Pr(a,b) = p(a)*p(b), > > once all common causal factors have been taken into account. > > We then consider the expression S = <a0b0> + <a0b1> + <a1b0> - <a1b1> for > measurement settings 0 and 1 and outcomes a,b in the range (-1, +1). If the > joint probabilities all satisfy the factorization condition associated with > the locality decomposition, we then have that > > S = <a0b0> + <a0b1> + <a1b0> - <a1b1> <= 2. > > This is the Clauser-Horne-Shimony-Holt (CHSH) inequality. The details on > the proof of this inequality, under the assumption of locality, is given in > the Brunner *et al.* reference above. > This inequality depends only on the assumption of locality as implemented > in the factorizabitity condition. It is easily shown that quantum > mechanical correlations violate this inequality: S = 2sqrt(2) > 2. The > conclusion is that quantum mechanics itself, in any interpretation or > model, is non-local. This conclusion does not depend on any assumptions > about realism or determinism. > > I see that Russell Standish has a recent post that also states that Bell's > theorem depends on assumptions of Realism and Determinism. Russell is just > as wrong about this as is John Clark. Bell's theorem depends only on the > assumption of locality, as proved above. > > Bruc > > Thank you. That's what I thought. AG > > > How is non-local defined? Does it imply instantaneous, or faster than > light transference of information? AG > I defined non-local above: whatever happens at A does not affect B and *vice versa*. It has nothing to do with faster-than-light transfer of information. If there was some FTL transfer between A and B, then the effect would be local. The idea that non-locality means FTL effects is a common confusion. That idea is totally wrong. Bruce -- 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 [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAFxXSLRHvRNbXpVdLPaMqwCkAcF2k9mjN3uSADyVM1EYvhGtwQ%40mail.gmail.com.
