On Sat, Aug 17, 2019 at 11:00 PM Bruno Marchal <marc...@ulb.ac.be> wrote:
> Brent, Bruce, > > On 16 Aug 2019, at 22:26, 'Brent Meeker' via Everything List < > everything-list@googlegroups.com> wrote: > > On 8/16/2019 4:23 AM, Bruno Marchal wrote: > > On 16 Aug 2019, at 03:27, 'Brent Meeker' via Everything List < > everything-list@googlegroups.com> wrote: > > > On 8/15/2019 5:06 PM, Bruce Kellett wrote: > > On Fri, Aug 16, 2019 at 9:25 AM Lawrence Crowell < > goldenfieldquaterni...@gmail.com> wrote: > >> I started reading this. It looks similar to the PR box argument. >> > > I have skimmed through it. It seems that Alice and Bob both split locally > according to the results they get, but then rely on magic to prevent the > incorrect pairs ever meeting. > > > I think you can interpret it as decoherence spreads at light speed from > Alice's measurement event and decoheres Bob's system when it comes within > the future light cone of Alice's measurement....and vice versa, which is > why it needs to assume MWI to maintain symmetry between Alice and Bob. > > > That is my understanding. That explains entirely, it seems to me, the > violation of Bell’s inequality in a local, but multi-versal type of > reality. When Alice and Bob separates, they simply never meet again, but > both can meet their correlated counterparts. Each Alice and each Bob can > meet only their correlates, that they enforce by decoherence, at a speed > lower than light. > > > But as Bruce says, it's a kind of magic as stated. To not be magic there > must be some physical interactions communicating Alice's result to Bob's > system: Photons would the obvious candidate, but how exactly do they > interact with Bob and his system to make them orthogonal to one of Alice's > results and not the other? > > > The state is ud - du, for d = down and u = up, with the usual sqrt(2) = 1. > > The idea is that when Alice see her photon being u, she knows that > whatever she will be interact with will be consistent wit her photon being > u and with bob photon being d, including the bob she could ever manifest > herself relatively. > That is exactly the magic that needs to be explained. > And reciprocally with Bob. It is just that when Alice see u, it means that > her accessible histories will all be consistent with u for her photon and d > for bob’s photon. If Bob sees u to, that will be the same: he knows that he > will meet Alice having seen d. Both possibilities will exist. The Alices > seeing u will access a world with Bob seeing d. The Alice seeing d, will > access a world with Bob seeing u. The same for Bob. Both Alices and Bobs > observations will spread toward each other at the speed of light, or > slower, and no physical influence exist at all. They both only localise > themselves in the multiverse, at different possible cosmic branches. > What makes a history "accessible"? You have offered only magic to rule out histories that violate the basic conservation rules. The magic comes only from the idea that there is one Alice and one Bob, > which would make this reasoning obviously invalid, or introduce faster than > light physical influence. > The argument does not depend on any "one world" assumption. The problem is clearly present even in the Everettian setting, when there are copies of Alice and Bob who see each result. These always exist, since both up and down results are always possible for any measurement on the separated singlet particles. > A quantum state does not describe a world, but is only an indexical map, > for a subject, of the histories that he/she can access to. ud-du means > only, to Alice and Bob, that they will always means their corresponding > correlated counterpart, whatever they found. > Given the miracle that occurs at this step in your account. > Even if we give sense to “they both find u”, each of us will meet they > counterparts, which they can interact with when meeting again, having > found d. > You are not convincing anyone other than yourself here, Bruno. 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLRbaP3K_VTybf6DtG%3D_Aq4hDgKGa9JzoRzZ6-TsoXEG8Q%40mail.gmail.com.
