> On 7 Aug 2019, at 15:18, Bruce Kellett <[email protected]> wrote: > > On Wed, Aug 7, 2019 at 7:48 PM Bruno Marchal <[email protected] > <mailto:[email protected]>> wrote: > On 7 Aug 2019, at 06:08, Bruce Kellett <[email protected] > <mailto:[email protected]>> wrote: >> >> Unitary evolution is an assumption. > Yes. It is called Quantum Mechanics (without collapse). > > No, it is actually just the Schroedinger equation. This works in certain > circumstances, but its universal validity has never been tested -- it is just > an unproven assumption.
All theories about any reality are “just” unproven assumption. But that is why we test it, and all modified QM so as to make the superposition disappear somewhere have been refuted. > >> It is manifestly violated in essentially every experiment that is performed. >> As I said, it serves no useful purpose to maintain that the superposition >> persists after a definite result has been obtained. It might satisfy your >> existential angst, but it has no role in physics. > Physics is not metaphysics, especially if we are asked to not try to figure > out what is happening. > > We figure out what is happening by forming theories that can be used to > predict the future. We eschew metaphysics, which is figuring out the > unknowable. So why bring unknowable things in physics then. Also, metaphysics is not on the unknowable, it is how to connect all the kwowable things with some possible ontology. If this imposes some unknowability, let it be. We cannot throw it out just by wishes. We can believe in big numbers being prime or not, even if we will never been able to decide and know which is which. > > The whole point of Everett is to regain consistency of QM, without collapse, > and it explains well the “illusion” of definite outcomes, which already does > not exist in arithmetic. > > Everett has many holes. It does not predict how to calculate probabilities. That is debatable. > It does not explain why we get singular outcomes, That is false. It explains it entirely by using the mechanist hypothesis. > and it does not even begin to answer the fundamental problem of the preferred > basis for observation. I disagree with this. Like with digital mechanism, you can choose any base (resp. Universal system) to describe the global (observed + observer) situation. Then from the first person view, some base (res. Universal system) can and do take more importance than others. > > You seem to want to change the theory to save the illusion of definite > outcome. > > Definite outcomes are not an illusion -- they are the reality that is > observed, which it is the purpose of physics to explain. How do you detect the singleness of an outcome? > > Not only you need to abandon Mechanism (as you do), but here it looks you > need to abandon QM, or to re-introduce some non unitary evolution in nature, > but we know that this has never work, and it transforms non locality into > action at a distance, also, not quite compatible with relativity. > > There are other possibilities to get from unitary evolution to the observed > outcomes. I refer you again to Zurek for some substantial recent advances on > these questions. Namely, einselection, envariance, and quantum Darwinism, > with the environment as witness. >From my reading of Zurek, he explains a lot, but stay in the non-collapse >theory, and the superpositions never disappear. They just are explained to be >quickly non accessible, justifying the local quasi-classicalness of physics. 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 [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAFxXSLTpqcNCXePXriP02haJaFcyHkcEk4Xd4m%2BqvCAbMs_zxA%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAFxXSLTpqcNCXePXriP02haJaFcyHkcEk4Xd4m%2BqvCAbMs_zxA%40mail.gmail.com?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/3838966C-DCC0-498C-B2E1-F87FE2D2F2A1%40ulb.ac.be.
