On Thu, Nov 28, 2019 at 8:48 AM 'Brent Meeker' via Everything List < everything-list@googlegroups.com> wrote:
> On 11/27/2019 4:27 AM, Bruce Kellett wrote: > I don't think you have seen the point I am trying to make. > > > I don't think I do either. > After overnight reflection I am no longer sure that there is a point! The starting point was the section on page 173 of Carroll's new book. I didn't think that that was actually a satisfactory answer to the question of energy conservation in MWI: energy is conserved in the global wave function by unitarity, but when there is a split in one branch, where does the energy of the other branches come from? The answer given is that the original energy is split according to the Born weights. That, at least, gives the global conservation. So half the original energy in my laboratory goes into the branch that sees spin-up in an S-G experiment, and half goes into the spin-down branch. Why am I not aware of this? I think the answer would be that it is the energy of the whole of the original branch that is split and that branch extends over time, so it looks as though the split occurs before the spin measurement -- at least as far as energy is concerned. So the picture that emerges is that in any superposition, the energy is split between components according to the Born weights, whether a measurement involving decoherence is made or not. Whether such an idea is even coherent is not clear. But that seems to be what MWI is committed to. Certainly we think energy is (locally) conserved in the world we observe, > which according to MWI is only one branch. So either energy is created in > order supply it for all the other branches, or there's some scaling > principle (which LC seems to suggest) such that if everything in a branch > is scaled to the appropriate probability, including the energy, then there > will be no observable difference. The latter is why I brought the > half-silvered mirror case, since it's not just energy that is conserved, > but the energy-momentum. And there's angular momentum too, and charge. > It's not just energy. > I think your 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? Simple scaling as with energy would seem not to work. 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/CAFxXSLRN42ZV7AaejcS9VXP3bP5Jm2OhumUiZaAkuqSWddWM-Q%40mail.gmail.com.
