> On 8 Aug 2019, at 01:44, Bruce Kellett <[email protected]> wrote: > > On Wed, Aug 7, 2019 at 11:52 PM Bruno Marchal <[email protected] > <mailto:[email protected]>> wrote: > On 7 Aug 2019, at 15:18, Bruce Kellett <[email protected] > <mailto:[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. > > No, not all have been refuted.
Right. I was thinking to the local theories. > What has been refuted is the idea that you can observe a superposition > between macroscopic objects (such as dead and alive cats). That follows directly from Everett QM. > All attempts to produce such superpositions have failed. I think it has been succeeded with big molecules (C_60), and superconductors. But it happens of course all the time, it is just that we cannot observe them directly, nor made them interfering without erasing our memories. H is just too small, but in QM without collapse, the superposition never disappear: they only get contagious to the observer and then we can explain why the observer does not feel the split, nor can he interact with the superposed state of itself. > The fact that you can write down an equation that seems to express such a > superposition does not mean that the superposition actually exists. Of course, we can introduce some collapse. But I talk about QM without collapse. > Explaining the absence of such superpositions is the central problem in the > foundations of quantum mechanics. It is the "preferred basis problem" in > essence. And this is the problem the Everettt did not solve. He does solve that, Imo. The base problem comes from a too much naïve conception of worlds, where Everett makes clear all subsystem can be seen as an observer of the rest of the system, and all relative sates are occurring. That is well re-explained in the video I just mentioned (with Susskind). 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/CAFxXSLT244s0AN%3DKNL5ZPeb3sFNZxCzT%2BzLR2-PA93vPoqQkEw%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAFxXSLT244s0AN%3DKNL5ZPeb3sFNZxCzT%2BzLR2-PA93vPoqQkEw%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/3E87C10B-95BA-4052-9A72-1C5D098E5D11%40ulb.ac.be.
