Like what? As far as I know (I can't claim I've actually studied this in much depth), the only real issue with the Everett interpretation is the current lack of a good justification of the Born rule. In "measurements", The Everett interpretation predicts a superposition of all the possible measurement outcomes entangled with the corresponding states of the observer. This superposition has a weighting and intuitively it's natural to take this weighting as the perceived probability associated with each branch, but there's no obvious way of reconciling this result with any definition of probability. I thought that was exactly the point I was making: a theory should apply at every scale by virtue of the fact that it applies at the most fundamental scale. So it shouldn't be necessary to postulate explicit laws for the macroscopic world (eg. concerning macroscopic observers and measurements). The behaviour of the macroscopic world should already be completely determined by the behaviour of the microscopic world. As it happens, the Everett interpretation technically is deterministic (because the Schrödinger equation is deterministic), though I don't really consider that a selling point: you get it at the cost of all the measurement outcomes occurring (the "many worlds"). As for realism: in one sense yes, I have an affinity for "realistic" theories, but I don't require it to apply to the entities of classical mechanics. I'm quite happy to think of quantum states as being "real". I'm not motivated by interpretations that eg. try to simultaneously attribute both a definite position and momentum to a particle - I just think of the particle as "really" being distributed in position/momentum space.
As far as I know, the Everett interpretation is a local interpretation of quantum theory (or at least can be, provided the Schrödinger equation is local). I'm not sure offhand, but I'd imagine it escapes Bell's theorem through a form of the detection loophole: an experimental outcome in the Copenhagen interpretation is only a single "branch" of the universal wavefunction in the Everett interpretation, and not the complete final state. If that's true, then I'd argue by extension that even non-local interpretations of quantum theory don't violate locality in a way that could lead to causal ambiguities, because they all make the same predictions as a local theory. There's an often stated intuitive argument that collapsing an entangled state doesn't violate SR because no "information" is ever conveyed. The existence of a local interpretation of QM could provide a way of justifying this argument.
Ahh I misread your original post. With this clarification then I think we agree on all fundamentals...Please Register or Log in to view the hidden image! Yes, you've basically hit on my problem with MWI. Most people can comprehend the branching concept (i.e. a half-silvered mirror). But what about a 2/3 silvered mirror? Are 3 worlds created, or 2 with "differing probabilities"? What is the mechanism which determines the likelihood of an observer experiencing one world over another? (additional axioms) What about an electron cloud? If you couple MWI with the claim that there is no wave function collapse you're left with, basically, an infinite number of universes based on the existence of a single electron! I'm sorry bro but at some point you just have to say "yuck". (I must admit, however, that ALL QM interpretations make me say "yuck"...it's just a matter of degree).
My very vague and you-can-bet-it's-wrong-or-twisted pop-sci understanding was that Everett described something like an infinite-dimensional continuum, that the 2-branch case was the simplest special case, and that the probability density of various states in the continuum was well defined by the shared elements of all QM interpretations (ie the mathematical model). I can understand your "yuck" reaction, but I find the idea pretty reasonable if I think of it in terms of more dimensions. Here's an analogy: Imagine a flat two dimensional world. Now give it some tiny thickness. How many distinct-but-connected two dimensional worlds are there now in that very thin three dimensional world? This analogy is weak. I think it is made closer if the extra dimension is timelike rather than spacelike, but I don't present this as an analytical model anyway - more like a very rough mental picture for the non-professional. Anyway. I don't know what I'm talking about here, so I'll prepare to be put down by those who do. :fright:
Maybe I've misunderstood your point, but I think this statement is wrong. For example, quantum field theories such as QED, QCD, electroweak and the full standard model are both quantum mechanical and relativistic. If you don't like the fact that I'm talking about fields rather than point particles you can think of the Dirac equation or the Klein Gordon equation as quantum particle wave equations.
With respect, I think you are conflating the wavefunction amplitude with an actual mechanism that determines which world we experience rather than being a mathematical tool. I guess I'm not saying such a mechanism doesn't exist, I was just pointing out to przyk that its existence would be required. (BTW it's not required in my interpretation) Actually...I can see what you're saying and it does help. You're saying that the extra dimensions aren't discrete, but rather smeared together just as we picture the electron cloud itself. Something to keep in mind: Each observer experiences Reality in its entirety as a discrete object. Your 2D analogy works fine with a single electron, but now add another...both electrons, in all of their possible states, must be potentially and discretely observable together. This raises the number of discrete Realities to (# of single electron states)^2. Or, using your analogy, a new dimension must be added for each electron! When trying to conceive of the number of dimensions involved I keep hearing the guy from Space Balls saying "They've gone PLAID!" Please Register or Log in to view the hidden image! Isn't there some sort of "appeal to thriftiness" in Physics? (actually I think there is, I just can't remember the term...) Quadraphonics, you are right that there is an issue for interpretations involving the wavefunction collapse. Note that the Everett Interpretation side steps this issue (as does my own).
I have never had much problem with the "wave function's collapse" as have the following POV wrt this: An inititial wave function which is a superposition of several Eigen functions begins to interact with potentials not part of its earlier system. - I.e. the Hamiltonian of the system is starting to change. It seems entirely reasonable to me that this is like a perturbation to the original system wave function. That perturbation can hardly be expected to change all the individual eigen function the same way, yet the probability of a measurement producing one of the possible eigen values remains unity. I.e. the relative strength of the various eigen function in the composite wave function will change. When the composite wave function evolves into a pure single eigen functions (what people call the collapse) yes that is the eigne value the measurement will have. SUMMARY: The measurement's interactions are just perturbing the original mixed set of eigen funcions until it becomes one pure eigen function for the classical world to observe. In the classical world, for example, the spin must be either up or down, can not be a mix like it can be in the QM world/ state. It is not that the "wave functions collapse" for no reason - it was perturbed but the potential (changing Hamiltonian) of the interaction with the measurement apparatus.
I don't think there's anything that defines a specific world that is more real than any other. You experience the particular world you are in. In other worlds, "you" have other experiences. You have many futures, if that makes sense. (I don't know if that implies you have many pasts... if so, it would have to be much less/fewer, since your "set of pasts" would only include those that led to this exact present state.) But yeah... I'm just musing, speculating, and way over-stretching from my ill-informed armchair, so I should probably butt out. Something to keep in mind: Each observer experiences Reality in its entirety as a discrete object. Your 2D analogy works fine with a single electron, but now add another...both electrons, in all of their possible states, must be potentially and discretely observable together. This raises the number of discrete Realities to (# of single electron states)^2. Or, using your analogy, a new dimension must be added for each electron![/quote] Right. Infinite-dimensional continuum. Parsimony, or Occam/Ockham's razor: Entities must not be multiplied beyond necessity (William of Ockham) We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. (Isaac Newton) Everything should be kept as simple as possible, but no simpler. (Albert Einstein) I think that postulating unlimited dimensions to explain the natural world is no less parsiminous than postulating unlimited electrons. Ie as long as each electron/dimension is described using the same model, they're not separate entities in the context of Occam's razor.
Yeah, that's correct. Something along those lines. Bell's theorem says that you can't have both locality and counterfactual definiteness. So, interpretations tend to discard one or the other. It's apparently popular to discard CFD (as the MWI does), since people have an easier time seeing how to square that with relativity (although, again, it's been shown that Bohm can be squared with relativity as well, if less obviously). The thing is that counterfactual definiteness is not really any less intuitively dispensible than locality. Both are elements of what we'd usually think of as comprising "realism." Abandoning CFD means that the moon really isn't there when you aren't looking at it. Another option is to abandon both locality and CFD, but that seems like overkill.
We are smart in our own ways. Besides, by clique, my definition of it here is that you cannot have an informed opinion on a topic if you don't know that topic to the standards the elite group know it to. That was one of my biggest problems here. I can accept when I am wrong, once I have investigated the opposing claims - until then one keeps to their own methodologies and ways of thought. That is just the way a human being is built, unless you soak things in like a sponge and accept things on face value.
Modern quantum theory has put the moon claim to the test. Recent confirmation proved niether Einstein or Bohr correct - both of them where somewhere ''in between'' the right answer. Apparently the quantum world can disappear when not being observed, but equally they do not disappear off the map - they can show up in places where they shouldn't be. This was performed using entangled photons.
There's a deeper issue here, and it involves the theories themselves (rather than their interpretations). Until we have a successful theory of quantum gravity, we're getting somewhat ahead of ourselves in worrying about what an interpretation thereof ought to look like. Not that metaphysics can't guide advances in physics, but I want to emphasize that the problem is much deeper than providing an interpretation of both QM and GR, since as of yet there is no successful theory that includes both QM and GR. But as to MWI: you're correct that it avoids clashing with SR by remaining local. But the question remains of how to square it with gravity. This is beyond my pay grade, but my understanding is that if quantum gravity introduces any nonlinearity (which seems likely), MWI will be immediately ruled out.
In 4 dimensions Rab describes the change in volume of a small ball of material particles, it's like a pressure equation in 3 dimensions.
The MWI describes the different "branches" as superoposed states in a single universal wavefunction, each with a different amplitude. For example, if someone observed whether or not a photon passed through a 2/3 silvered mirror, the MWI would predict a superposition of two states (the "branches"), one with an amplitude of \(\frac{1}{\sqrt{3}}\) and the other with an amplitude of \(\frac{\sqrt{2}}{\sqrt{3}}\). So the MWI naturally provides a weighting associated with each branch. I just don't know a good argument which explains why we perceive this weighting as a probability, though I'm not prepared to rule it out as impossible. One avenue for instance might be to consider a succession of measurements, and show that the branches containing "unlikely" combinations of results disappear (approach zero amplitude) in the limit of an infinite number of experiments. It may not be very convincing, but when I think too much about it I run into the same sort of difficulty with the concept of probability anyway. Well in the language of QM, it's a single universe containing a single electron which is in a superposition of position states.
Are you sure? As I understand it, Bell's theorem is only supposed to rule out what Bell called "local causality". There's an article which explains this point here (I had difficulties for a while with the technical nature of Bell's theorem; for me this is the article which finally switched the lightbulb on). It heavily references Bell's own "Theory of Local Beables" (available online here). Basically, Bell inequalities are based on the assumption that observed joint conditional probabilities \(P(A,\,B\,|\,a,\,b)\) (where A and B are measurement results and a and b are corresponding detector settings) factorise as \(P(A,\,B\,|\,a,\,b) \,=\, \int \text{d}\lambda \, \rho(\lambda) \, P(A\,|\,a;\,\lambda) \, P(B\,|\,b;\,\lambda) \;,\)which is obtained by applying Bell's own concept of local causality. Since particular results A and B in eg. the Copenhagen interpretation aren't the complete result in the MWI, Bell's theorem as it is usually applied doesn't concern the MWI, I think Bell's theorem might still apply to the MWI in a way, as long as it's applied to what the MWI considers its fundamental predictions (eg. the value of the "universal wavefunction" at particular points in space-time).
An observer is a subjectivity, through any instrument, purposefully witnessing [observing] a time, place, object and/or entity. A note I'd like to make regarding "quantum" is that, "quantum", with all its characteristics, is imperceivable until a mind is prepared to conceive of such and operate with "quantum" capabilities itself. Such is true for all things as well, the mind must be both receptive to and maleable to match what is going on to be able to perceive it. Truths abound throughout the Universe, yet people, often a majority, are indoctrinated to deny such things are true, factual or extant at all. Covering one's eyes will not make an object disappear, pluggin one's ears will not prevent humanity from making progress, just retard oneself with inertia as the Universe progresses further. Tantrika practice is operative within quantum realms and continuities and prepares the tantrika practitioner to awaken to creative potentialities, in every realm of life, including physics, as inert as that is, and especially in psychic and psycho-spiritual realms, more subtle than physics.
Observations from in our beings, may be subjective by psychological evaluation, but in quantum mechanics, a true observer requires not the term of subjectivity.
Dude, if you have to ask, you can't afford it.:deal:Please Register or Log in to view the hidden image!
Oh wow I wasn't aware of that. Are you familiar with how MWI would fall to nonlinearity? IMHO MWI is structured to be virtually unfalsifiable..."everything exists, period, and you can't prove otherwise".
