On Sunday, February 9, 2020 at 3:37:51 AM UTC-7, Bruce wrote: > > On Sun, Feb 9, 2020 at 7:48 PM smitra <smi...@zonnet.nl <javascript:>> > wrote: > >> On 08-02-2020 07:00, Bruce Kellett wrote: >> > On Sat, Feb 8, 2020 at 4:21 PM smitra <smi...@zonnet.nl <javascript:>> >> wrote: >> > >> >> On 08-02-2020 05:19, Bruce Kellett wrote: >> >> >> >>> No, I am suggesting that Many-worlds is a failed theory, unable to >> >>> account for everyday experience. A stochastic single-world theory >> >> is >> >>> perfectly able to account for what we see. >> >>> >> >>> Bruce >> >> >> >> Stochastic single word theories make predictions that violate those >> >> of >> >> quantum mechanics. >> > >> > No they don't. When have violations of the quantum predictions been >> > observed? >> >> A single world theory must violate unitary time evolution, it has to >> assume a violation of the Schrodinger equation. But there is no >> experimental evidence for violations of the Schrodinger equation. While >> one can make such assumptions and develop a formalism based on this, the >> issue is then that in the absence of experimental proof that the >> Schrodinger equation is going to be violated, one should not claim that >> such a model is superior than another model that doesn't imply any new >> physics. >> > > So what. If Everettian QM doesn't work, as it has been shown to fail in > that is does not recover normal scientific practice, then one must look to > alternative theories. I have not advocated any particular theory, but a > break down of unitary evolution is not such a big deal -- it is what we > observe every day, after all. This is the heart of the quantum measurement > problem. >
*You claim unitary evolution breaks down in the measurement problem. CMIIAW, but don't you also affirm decoherence theory where unitary evolution does NOT breakdown in the measurement process? Which is it, or do I misconstrue your positions? TIA, AG * > > The MWI may have some philosophical weaknesses like the derivation of >> the Born rule but the pragmatic variant of it where you just assume the >> Born rule is clearly superior to any other model where you're going to >> just assume that the known laws of physics are going to be violated to >> get to a model that to you looks more desirable from a philosophical >> point of view. >> > > The trouble is that even postulating the Born rule, ad hoc as in > Copenhagen, does not get you out of the problems with Everett. As long as > one follows Everett and assumes one branch for each component of the > superposition, one is going to fail to explain normal scientific practice. > If one follows Brent and Bruno and assumes that there are multiple branches > for each experimental result, then one has lost touch with the Schrodinger > equation anyway, Everett is out of the window, and there are still problems > with the definition of probability. > > It is probably a matter of which is the least bad theory at the moment. > None of the available approaches is entirely satisfactory. But that is not > an unusual situation in the development of physics..... > >> > >> >> If the MWI (in the general sense of there existing a >> >> multiverse rather than any details of how to derive the Born rule) >> >> is >> >> not correct, then that's hard to reconcile with known experimental >> >> results. >> > >> > All experimental results to date are consistent with a single-world >> > theory. There are several possibilities for such a theory, but to >> > date, experiment does not distinguish between them. >> >> Single world theories require a violation of unitary time evolution of a >> perfectly isolated system. No experiment has ever observed this. >> > >> >> New physics that so far has never been observed needs to be >> >> assumed just to get rid of the Many Worlds. Also, this new physics >> >> should appear not at the as of yet unprobed high energies where the >> >> known laws of physics could plausibly break down, instead it would >> >> have >> >> to appear at the mesoscopic or macroscopic scale where the laws of >> >> physics are essentially fixed. >> > >> > Bohm's theory does not require as-yet-unobserved new physics. GRW do >> > postulate a new physical interaction, but that is below the level of >> > current experimental detectability. >> >> Bohm theory is not equivalent to QM, it only becomes equivalent to QM if >> one imposes a condition known as "quantum equilibrium". In general, Bohm >> theory in a condition of quantum non-equilibrium leads to violations of >> the Born rule. See here for details: >> >> https://en.wikipedia.org/wiki/Quantum_non-equilibrium > > > There is not evidence for any of this type of worry, either. So why bring > it up? > > Then without any experimental evidence for the additional features of >> Bohm theory such as the signatures of quantum non-equilibrium, why would >> be prefer it over and above a theory that doesn't make such assumptions? >> One would have to have very strong theoretical objections against the >> theory. In case of the Standard Model one can predict that it will break >> down at very high energies. But I don't see why the MWI in the pragmatic >> sense where one assumes the Born rule is so bad that it merits >> considering alternative theories, particularly if those alternative >> theories make lots of unverified assumptions about new physics in >> domains where new physics is thought to be unlikely to appear. >> > > Who says so? Sounds like special pleading to me..... > >> > >> > Besides, why should you assume that the Schrodinger equation is the >> > ultimate physical law? >> >> It may be false, but absent experimental evidence that it is indeed >> false, theories that imply that it's false shouldn't get the benefit of >> the doubt just because they imply a single world. >> > > > Maybe single world theories are better adapted to explaining our ordinary > experience -- and explaining everyday experience is, in the final analysis, > the aim of any scientific theory. > > 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/54304959-15b3-4aef-a22e-3f7cd4c3fd66%40googlegroups.com.
