On Sun, 17 Jan 2021 at 12:47 am, 'scerir' via Everything List < [email protected]> wrote:
> Imagine a spin-1/2 particle described by the *superposition* psi = > sqrt(1/2)[(s+)_z +(s-)_z] . > > If the x-component of spin is measured by passing the spin-1/2 particle > through a Stern-Gerlach with its field oriented along the x-axis, the > particle will > *always* emerge 'up'. Why? It is a superposition, why not MWI? > That article does not show that MWI predicts anything other than what we observe or what Copenhagen predicts. It adds to the superposition the fact that M measures the spin as up then says “so if the spin is now definitely up then what M’ observes will not depend on probability.” But that whole argument presupposes a collapse model where e and M have some definite value once M measures e by before M’ measures the state of M. What MWI says is that M remains in a superposition of all outcomes until M’ interacts with it. The stipulation that e an M are in a definite, singular state before being measured is a red herring. > > > Il 16/01/2021 13:25 Pierz Newton-John <[email protected]> ha scritto: > > > > > On Sat, 16 Jan 2021 at 8:16 pm, 'scerir' via Everything List < > [email protected]> wrote: > > Pierz wrote: "If you want to argue against the internal logic of MWI, you > have to start by accepting what it proposes then proceeding to demonstrate > how that leads to internal inconsistency." > > They show that MWI is inconsistent, in the Schroedinger picture. > https://link.springer.com/article/10.1007%2FBF00763476 > > > Well that argument at least demonstrates some understanding of MWI, unlike > AG. But I don’t think it’s a good argument at all. Has the system M > decohered and thus become entangled with M’ after M measures the spin? If > so, then M and M’ are already on the same branch/ in the same world as one > another and there is only one possible measurement M’ can make. The outcome > is not subject to probability. If on the other hand, the system M has not > decohered with the common environment of M’, then M remains in a > superposition of up and down measurement states until measured by M’ and it > does not make sense to say that either the electron or M itself are in a > definite state with respect to M’. Both branches/ worlds exist and M’ has > not yet split on the outcome. It’s a pretty basic point. > > > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Everything List" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/everything-list/xsl8cSDT4M8/unsubscribe. > > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/53333396.1238733.1610788558703%40mail1.libero.it > <https://groups.google.com/d/msgid/everything-list/53333396.1238733.1610788558703%40mail1.libero.it?utm_medium=email&utm_source=footer>. > > > > -- > > 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/CAArMS02UZAEHpwcVKp%2B0GitF%3DAa-FPwBqKZUco2doyV1Z3w0jg%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAArMS02UZAEHpwcVKp%2B0GitF%3DAa-FPwBqKZUco2doyV1Z3w0jg%40mail.gmail.com?utm_medium=email&utm_source=footer>. > > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Everything List" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/everything-list/xsl8cSDT4M8/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/610945189.1243543.1610804823781%40mail1.libero.it > <https://groups.google.com/d/msgid/everything-list/610945189.1243543.1610804823781%40mail1.libero.it?utm_medium=email&utm_source=footer> > . > -- 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/CAArMS03KdQutDtH0fK3V97Ca038d2Gm3GAHQzngUZfmEjrg2tQ%40mail.gmail.com.
