On Thu, Nov 28, 2019 at 11:49 AM 'Brent Meeker' via Everything List < everything-list@googlegroups.com> wrote:
> On 11/27/2019 4:05 PM, Bruce Kellett wrote: > > On Thu, Nov 28, 2019 at 10:47 AM Pierz <pier...@gmail.com> wrote: > >> On Thursday, November 28, 2019 at 9:51:55 AM UTC+11, Bruce wrote: >>> >>> On Thu, Nov 28, 2019 at 9:29 AM John Clark <johnk...@gmail.com> wrote: >>> >>>> On Wed, Nov 27, 2019 at 5:13 PM Bruce Kellett <bhkel...@gmail.com> >>>> wrote: >>>> >>>> *> I think your* [Brent Meeker] *point about other conservation laws >>>>> is interesting -- especially charge. How would you divide the charge of a >>>>> state among the superposed basis states according to the Born rule and get >>>>> charge conservation in every branch?* >>>> >>>> >>>> Our branch of the multiverse is electrically neutral and it seems >>>> likely all of them are, so preserving conservation of charge doesn't seem >>>> like much of a problem. >>>> >>> >>> >>> Consider firing an electron at a screen. There are a very large number >>> of sub-branches created -- one for every position that the electron can >>> land. There was only one negative charge originally -- now there are a very >>> large number. Where did the extra charges come from? >>> >>> I think it's a misapplication of rules that empirically apply (locally, >> as JC points out) within branches, which is the only world we ever directly >> know. "Where did the extra charges come from?" is the same question as >> "where did the extra matter come from?", yet that is simply what happens *ex >> hypothesi >> *in MWI. We observe that time evolution is unitary - and that >> observation is naturally always within the context of individual branches. >> Therefore it seems to me to be over-extending the principle to even try to >> apply that rule across branches as well. Perhaps there is some >> "renormalization" we can do to make a preserved quantity, but why bother - >> just so that we can say, hey, look at that, we preserved it!? I tried to >> explain MWI to a physics-naive friend once and she said, "but then you'd >> see the other copies!" (or something like that). Well of course that is >> silly, but fundamentally it's the same mistake - thinking that principles >> that apply across individual branches must also apply between them. >> > > Fair enough. That sounds reasonable. The trouble is that conservation in > the wave function comes from unitary evolution. And unitary evolution > applies only to the universal wave function -- time development on > individual branches is not unitary. > > > Although it's not in the way contemplated for MWI, it has been known since > Wigner that some measurements will not conserve energy (even locally) it > was proven in general for conserved quantities in the WAY theorem: > https://arxiv.org/pdf/1610.04607.pdf > Does not the Wigner result (and the WAY theorem) depend on the dubious assumption that since measurements are represent by hermitian operators, all hermitian operators correspond to measurements? Clearly, not all hermitian matrices commute with the Hamiltonian. 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/CAFxXSLTLqaq91woktm9zZA-BAtN9sZoiW6aZW5dwP1ecPT77rg%40mail.gmail.com.
