On Wed, Oct 2, 2019 at 1:52 PM 'Brent Meeker' via Everything List < [email protected]> wrote:
> On 10/1/2019 4:55 PM, Bruce Kellett wrote: > > On Wed, Oct 2, 2019 at 3:12 AM 'Brent Meeker' via Everything List < > [email protected]> wrote: > >> On 9/30/2019 11:06 PM, Bruce Kellett wrote: >> >> You say the light carrying the >>> information isn't coherent, but it's not just the light that carries the >>> information; it's information encoded in the wave function of the >>> environment. >> >> >> That information encoded in the wave function of the environment has to >> be coherent if the impossible branches are to cancel out. And that >> coherence must originate in the measurement interactions that Alice and Bob >> perform. And that is non-local, since Bob and Alice are space like >> separated. >> >> >> You're right. >> > > You're conceding? I expected more of an argument..... > > > I thought about it some more. > > You couldn't scan the relevant section of Carroll's book and send it to > me, could you? Please. I would like to see how Carroll attempts to get out > of the non-locality issue..... > > > Carroll doesn't try to deny non-locality. It's just that he draws a > diagram such as Bruno suggests in which the results of Alice and Bob > propagate futureward as waves of splitting which eventually overlap and the > results can be compared. Then he also draws the other diagram in which > there is a space-like hypersurface thru Alice and Bob's measurement events > (at the same time) and the universe splits then. He says it doesn't matter > which you use. > I don't really understand this. I would have to see the original text. Wallace does something similar with the diagram in which the results propagate along the forward light curve and the separate branches are formed according to the respective results. At least, he does this for the simpler case of independent measurements by Alice and Bob on non-entangled, independent spin states. Wallace clearly knows what would be required for a satisfactory explanation of the branch splitting and the formation of a set of joint results. He works through the independent case in detail, explaining it in terms of a third observer, Carol, who sits between Alice and Bob, and receives their results along the light cone. Carol receives Alice's results first (she is slightly closer to Alice), and splits in two: 'Carol-who-sees-Alice-up', and 'Carol-who-sees-Alice-down'. Then later, she receives Bob's results, and each branch splits again according to Bob's results of 'up' or 'down'. Leading to four branches in all. Wallace gives the weights, or probabilities, of these branches for Carol correctly, in terms of the original states that Alice and Bob measure, and the measurements they make. All of this is straightforward and conventional. But when he comes to analyse the case of entangled particles, he wimps out from this sort of detail and mutters vague generalities about the "forward propagation of the entanglement". My impression when I first read this was that Wallace, fully knowing what a comprehensive account would entail, intended to give a detailed analysis in the same form as he gave for the non-entangled case, drawing attention to the similarities and difference induced by the entanglement. But when he came to work this through, he found that he could not produce any such transparent account. So he fell back on vague generalities (as an admission of defeat!). Maybe I am maligning the man, but these sections of his book do read rather oddly -- promising a lot more than is actually delivered. 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 on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLST5Yvuc2PB5yOmiucQBeJ-uUv-SSMfm7Ycdi9xjN7U5A%40mail.gmail.com.
