Oh my god, I have almost 3000 likes!!! :love: — Kenosha Kid
Yes, I think this is what I meant. The first is relativism, the second pluralism, and they are equivalent. As I said, I encountered this first in a discussion on moral relativism versus objectivity, including pluralism, and I understood how the latter isn't just the former insisting it's the latter. — Kenosha Kid
Observation y depends on the value of x. — magritte
"The cat is dead" is true for Wigner's friend but not for Wigner. — Kenosha Kid
There is an interesting thing about that cat. Wigner's cat and his friend's cat are obviously not the same cat, as one is alive and the other is dead. Ontologically speaking, this is the only correct answer. People who claim that the there is but one cat are suffering from confusion. To expand, there are as many cats as there are observers."The cat is dead". The truth value of that depends on who you ask. — Kenosha Kid
one is alive and the other is dead. — magritte
Sorry about that! I'm only trying to make a point to Kenosha Kid there.Talk about the state of anything when it is not being observed is empty words. — Wayfarer
quantum mechanics.People who claim that the there is but one cat are suffering from — magritte
Talk about the state of anything when it is not being observed is empty words. — Wayfarer
you really want to elevate yourself to a condition of existence? Universalize self-dependence? :brow: Let's talk about Mars.
If this was just a story about the friend telling Wigner that the measurement has been done by, say, sending a photon, ignoring everything else, even that the measurement was a quantum one, would you say that this process of sending a photon from one system to another didn't entangle the two systems? — Kenosha Kid
The novelty of Deutsch’s proposal [10] lies in the possibility for Wigner to acquire direct knowledge on whether the friend has observed a definite outcome upon her measurement or not without revealing what outcome she has observed. The friend could open the laboratory in a manner that allowed communication (e.g., a specific message written on a piece of paper) to be passed outside to Wigner, keeping all other degrees of freedom fully isolated, as illustrated in Figure 1. Obviously, it is of central importance that the message does not contain any information concerning the specific observed outcome (which would destroy the coherence of state (1)), but merely an indication of the kind: “I have observed a definite outcome” or “I have not observed a definite outcome”. If the message is encoded in the state of system M, the overall state is:
(2)
since the state of the message is factorized out from the total state (I leave the option for the message “I have not observed a definite outcome” out, as it conflicts with our experience of the situation that we refer to as measurement and it also can be used to violate the bound on quantum state discrimination [8]). — A No-Go Theorem for Observer-Independent Facts - Caslav Brukner
In Section 8 I describe a thought experiment whose main purpose is to show how the conventional and Everett interpretations are in principle experimentally distinguishable. — Quantum Theory as a Universal Physical Theory - David Deutsch, 1985
The interference phenomenon seen by our observer at the end of the experiment requires the presence of both spin values, though he accurately remembers having known at a previous time that only one of them was present. He must infer that there was more than one copy of himself (and the atom) in existence at that time, and that these copies merged to form his present self.
He must infer that there was more than one copy of himself (and the atom) in existence at that time, and that these copies merged to form his present self.
"Once we have granted that any physical theory is essentially only a model for the world of experience,” Everett concluded in the unedited version of his dissertation, “we must renounce all hope of finding anything like the correct theory ... simply because the totality of experience is never accessible to us.” — The Many Worlds of Hugh Everett
I'm sorry, but I just find this really creepy. And I still would like to know what Deutsch would be obliged to admit if it were shown it could not be true. I mean, what's he frightened of? — Wayfarer
their [Physicists] attempts to see in the very inadequacy of the conventional interpretation of quantum theory a deep physical principle have often led physicists to adopt obscurantist, mystical, positivist, psychical, and other irrational world views. Undermining, as it thus does, the view that it is the task of physics to seek a systematic understanding of a real, objectively existing world, the widespread acceptance of the conventional interpretation cannot but have impeded the growth of knowledge in physics.
I note the posit of a 'real, objectively existing world'. Presumably this is not regarded as an axiom? It would seem a philosophical pre-supposition, at least. — Wayfarer
As DeWitt put it: ‘every quantum transition taking place on every star, in every galaxy, in every remote corner of the universe is splitting our local world on earth into myriads of copies’. Recall that this profusion is deemed necessary only because we don’t yet understand wavefunction collapse. It’s a way of avoiding the mathematical ungainliness of that lacuna. — Phillip Ball, Too Many Worlds
Good quote.Philip Ball is no fan of many worlds. He notes:
As DeWitt put it: ‘every quantum transition taking place on every star, in every galaxy, in every remote corner of the universe is splitting our local world on earth into myriads of copies’. Recall that this profusion is deemed necessary only because we don’t yet understand wavefunction collapse. It’s a way of avoiding the mathematical ungainliness of that lacuna.
— Phillip Ball, Too Many Worlds
Which is just how I see it. Again, for what it’s worth. — Wayfarer
Yes, this is what I meant regarding separability. In reality, it's not that clean: if you have two atoms, say, correlated by exchange of a photon, you cannot evolve them independently: it's a single many-body wavefunction describing the whole system, and the exchange and correlation parts of that are not trivial. — Kenosha Kid
The formalism above necessarily neglects the fact that Wigner and his friend are entangled anyway. — Kenosha Kid
What we should see in MWI is each branch evolving independently as if it were the whole universe. — Kenosha Kid
|Wigner>|friend>|spin up>|I've observed a definite outcome>
The above is what MWI (and unitary QM) predicts. — Andrew M
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