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> You seemingly consider one measurement and expect to see Born rule Huh??? No, of course not. The Born rule is about probabilities. It cannot manifest in a
by lisper 1y ago
> You seemingly consider one measurement and expect to see Born rule
Huh??? No, of course not. The Born rule is about probabilities. It cannot manifest in a single measurement.
> classical behavior emerges by tracing, mathematically, not as a physical process?
No. The mathematical description of classical outcomes emerges by tracing, which is to say, by discarding information. The physical interpretation of that is left open.
> In MWI classical behavior emerges as a physical process
That's right. MWI commits to a physical interpretation of the math. But there is no scientific or philosophical justification for this, and in fact, when you dig into the details all kinds of problems emerge that are swept under the rug by its proponents. Nonetheless, many MWI proponents insist that it is the One True Interpretation, including some who really ought to know better.
> each observer naturally observes their branch from inside, and it looks isolated from other branches.
Yes, I know. But this doesn't solve the problem. In order to get a mathematical description of me I have to trace the wave function in my preferred basis, which is to say, I have to throw out all of the other branches. And this is not just a computational hack. It's mathematically necessary. Discarding information is the only way to get classical, irreversible processes (like measurement) out of the unitary dynamics of the wave function. So a reasonable interpretation of the math is that I exist only if parallel universes don't. And I'm pretty sure I exist.
I'm not telling you this because I expect you to accept it, merely to show you that the MWI is not self-evidently the One True Interpretation.
- GoblinSlayer 1y agoIn the blog post you say that tracing lets you consider a subset of an entangled system in isolation from the rest of the system. That was consistent with MWI where states are isolated from each other and not discarded. Mathematically discarding isn't necessary, isolation is sufficient.
- lisper 1y agoSure. So? MWI is not mathematically untenable, it's just incomplete (because it can't account for the Born rule) and IMHO philosophically untenable because it requires that no experiment can demonstrate the existence of a fully isolated universe, i.e. a universe whose macroscopic configuration is different from ours [1]. This feature of the MWI is what I call an IPU -- an Invisible Pink Unicorn -- something that the theory insists exists despite the fact that the theory also requires it to be unmeasurable even in principle. If you want to believe it exists, fine. Just don't call it science, and definitely don't insist that anyone who doesn't accept it is being irrational. It's attitudes like that that turn Rationalism (with a capital R) into a cult. --- [1] https://blog.rongarret.info/2009/04/on-shadow-photons-and-real-unicorns.html https://blog.rongarret.info/2009/04/on-shadow-photons-and-re... (Note that I wrote this 16 years ago, so not everything is 100% accurate, but I stand by the central point.)
- GoblinSlayer 1y agoIn MWI the Born rule is a tendency of statistics of a long string of measurements. You tried to get this statistics from one measurement, which didn't work. If you want to see how MWI produces the Born rule, you should calculate statistics of a long string of measurements and see that this statistics is asymptotically close to Born statistics. Other branches can be demonstrated indirectly by 1) quantitatively verifying unitary dynamics, 2) indirectly observing branching, 3) demonstrating that other theories are wrong. Branches are just superposition, if you want to eliminate branches, you should eliminate superposition with pilot wave or superdeterminism or something like that. This kind of unobservability isn't unique to MWI, in general theory of relativity we observe only a part of the universe, the rest being beyond event horizon and is unobservable. Do you believe only observable part of the universe exists and beyond it nothing exists?
- lisper 1y ago> You tried to get this statistics from one measurement Huh??? When? > Other branches can be demonstrated Sure, that's just QM 101. What you cannot demonstrate experimentally, not even in principle, is the existence of other branches with different macroscopic configurations than our own. Such branches are IPUs.
- GoblinSlayer 1y ago>Huh??? When? In the blog post you linked above: >No, it isn't because it can't account for the Born rule. See: >https://blog.rongarret.info/2019/07/the-trouble-with-many-worlds.html https://blog.rongarret.info/2019/07/the-trouble-with-many-wo... >What you cannot demonstrate experimentally, not even in principle I provided 3 ways to demonstrate it experimentally, even in principle, not sure what problem you have.
- lisper 1y ago> In the blog post you linked above Again, huh??? Where in that blog post do I try to "get this [sic] statistics from one measurement"? > I provided 3 ways to demonstrate it experimentally, even in principle, not sure what problem you have. No, you didn't. You apparently don't understand what is meant by "branches with different macroscopic configurations than our own" and I don't have time to explain it to you. Sorry. Go read up on decoherence, and then come back and describe an experiment that can demonstrate the existence of a fully decohered branch. You can't, because if you could it would by definition not be fully docohered.