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If the Universal Wave Function definitely existed, would that mean the Many-Worlds Interpretation was automatically true or would it only imply that?

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  • $\begingroup$ No, correct me if I'm wrong but objective collapse theories also posit a universal wavefunction. $\endgroup$ Jun 9 '20 at 3:01
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It would imply that we are entities bound by the laws of quantum mechanics, and thus there are no truly classical observers to observe the system. The QM interpretations are only needed to explain their behavior with respect to a classical observer.

Decoherence based theories would be the natural winner.

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The concept of "wavefunction"is inherent in the definition of Quantum Mechanics,in the same way the concept of mass is inherent in the definition of classical mechanics: it is a mathematical function which is used to model data and predict physical behavior of matter at small dimensions .

Present physics modeling assumes that the underlying microscopic interactions obey quantum mechanical equations, and it has been shown that the classical theories emerge from this underlying level. In this sense a universal wave function, assuming extreme measurement accuracies, exists and has been modeled with the density matrix formalism .

[The many-worlds interpretation] (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wavefunction collapse. This implies that all possible outcomes of quantum measurements are physically realized in some "world" or universe

As in principle a universal wave function exists, the crucial word is "interpretation". It means that the proposal gives exactly the same numerical predictions for new studies , just a different way of interpreting the internal functions.

would that mean the Many-Worlds Interpretation was automatically true or would it only imply that?

The universal wavefunction exists, can be formulated mathematically . The mathematics is true, but the many-worlds interpretation of the mathematics is just a different optical angle,there are no new predictions to be able to distinguish if it is valid or not.

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  • $\begingroup$ Thank you for your answer. What I meant was specifically regarding what that quote said "(MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real", that being the objective existence of the UWF as more than just math. Like, does Copenhagen contradict EVERYTHING, including the observer being part of the UWF (cuz of measurement)? If I recall correctly Bohmian Mechanics has a UWF that is objectively real. If that last part is true then I guess that would answer my question, although I'm still wondering how it works for other interpretations. $\endgroup$ Jun 10 '20 at 9:37
  • $\begingroup$ @Thatpotatoisaspy Again I emphsize that "interpretation" means that the exact same predictions come from different mathematics. The Bohm hypothesis is an intepretation for non relativistic energies, but fails for relativistic ones, afaik.It has a pilot wave generating the probabilistic nature, but it is not possible to measure it independently (otherwise it would be a different theory to be checked for validity) $\endgroup$
    – anna v
    Jun 10 '20 at 9:43
  • $\begingroup$ Interesting. I’m running into a similar problem as Aristotles “prime mover” if you’ve ever heard of it. In Copenhagen afaik collapse occurs when an (presumably classical i think?) observer somehow affects a system externally, but if the UWF conception had any validity then if everything in the Universe was part of the UWF then what would cause a collapse to happen in the first place? There would be nothing external to the system to do it. This is all very confusing to me. $\endgroup$ Jun 10 '20 at 9:54
  • $\begingroup$ for "collapse" see my answer herehttps://physics.stackexchange.com/questions/263417/double-slit-experiment-evidence-of-wavefunction-collapse/263433#263433 $\endgroup$
    – anna v
    Jun 10 '20 at 10:55
  • $\begingroup$ Isn’t that at odds with the copenhagen interpretation? I presume you just take a different stance then. If i’m not wrong isn’t this referred to as QBism? $\endgroup$ Jun 10 '20 at 15:14

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