3 ms·
Totally agree. It's therapeutic to read this. Last I checked, many-worlds is a consequence of current quantum theory, not a postulate or additional axiom. Yet
by myridium 5y ago
Totally agree. It's therapeutic to read this.
Last I checked, many-worlds is a consequence of current quantum theory, not a postulate or additional axiom. Yet people treat it like such. Probably because it's 'spooky'. Then indeed it's ironic that they search for alternative explanations which try to say the same thing as many worlds but without saying 'many worlds'.
- naasking 5y ago> Last I checked, many-worlds is a consequence of current quantum theory, not a postulate or additional axiom. There is an additional postulate, namely that the state vector is the real world we inhabit. This may seem obvious to you and not amount to postulating much or anything with any substance, but that's a philosophical claim that isn't suggested by the physics. There are also the problems of deriving the Born rule from the existing postulates of MWI. Last I checked, the existing derivations are not fully satisfactory to most physicists.
- myridium 5y agoI'll have to look into those derivations. Thanks. > There is an additional postulate, namely that the state vector is the real world we inhabit. Well, yes, it's a model for the physical world. Refusing to accept that the state vector is the real world we inhabit is tantamount to rejecting the existence of an objective universe, in which case any discussion is moot, or to the outright rejection of quantum theory, which seems irrational. (i.e. "I don't believe the state vector represents our world, despite it being the best physical model of our time")
- naasking 5y ago> Well, yes, it's a model for the physical world. Refusing to accept that the state vector is the real world we inhabit is tantamount to rejecting the existence of an objective universe, in which case any discussion is moot Some physicists consider the wave function to be ontologically inadequate to explain the physical world. See the discussion of "bohmian mechanics being many worlds in denial" for some details and references: https://plato.stanford.edu/entries/qm-bohm/#ObjeResp https://plato.stanford.edu/entries/qm-bohm/#ObjeResp
- myridium 5y agoIt may be inadequate, but the consequences of quantum theory still apply without having to add new postulates. Among those consequences is many worlds.
- naasking 5y agoSaying it's ontologically inadequate means that it's insufficient to describe what we consider "real", and thus the wave function by itself cannot describe one world let alone many worlds.
- lmm 5y ago> There is an additional postulate, namely that the state vector is the real world we inhabit. This may seem obvious to you and not amount to postulating much or anything with any substance, but that's a philosophical claim that isn't suggested by the physics. Any interpretation has to postulate that something "is" the real world, in that sense. Postulating that there's an additional entity dependent on the wavefunction that "is" the real world (as e.g. pilot-wave theories do) is violating Occam's Razor. > There are also the problems of deriving the Born rule from the existing postulates of MWI. There are, but again, all interpretations have that problem, and adding more postulates just makes it worse. E.g. if you take a Copenhagen interpretation you have to derive the probability rule and a rule for what constitutes a "measurement" that triggers when the rule should be applied.
- naasking 5y ago> Postulating that there's an additional entity dependent on the wavefunction that "is" the real world (as e.g. pilot-wave theories do) is violating Occam's Razor. Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. Bohmian mechanics is kind of the dual of many worlds in this sense, and so requires no more postulates. > There are, but again, all interpretations have that problem Since you mentioned Bohmian mechanics, the Born rule was derived from the postulates a long time ago, and the Bohmian form of Schrodinger's equation is structured in a such a way that the quantum component goes to zero in the limit, thus reducing to classical mechanics.
- lmm 5y ago> Not really, because in Bohmian mechanics the wave function is nomological, ie. not real, and merely describes a law of motion. I don't see that that's a meaningful/objective distinction? The wavefunction is certainly physically meaningful in the sense that you can't predict experimental results without computing its behaviour (or something equivalent to it). I don't think that you can reduce your number of postulates by declaring parts of your theory "not real" - given that elementary particles are not directly observable, couldn't we just declare that e.g. electrons are "not real" and merely describe a law of experimental results? > Since you mentioned Bohmian mechanics, the Born rule was derived from the postulates a long time ago It's not really derived, rather something equivalent to the Born rule is included as one of those postulates. At some point you have to go from wavefunction to probability distribution, and you either make the rule for that an outright postulate or have some plausible but unsatisfactory argument about how dynamical evolution makes this the "right" rule. Different interpretations do this at different points, but they all have to do it somewhere.
- 8note 5y agoThere's is definitely an axiom built into many world's. Something along the lines of "things we don't observe are as valid and exist as much as things we do observe" That's an addition over the usual "things we observe exist"