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EPR experiments imply STR not correct?

  1. Feb 14, 2009 #1
    Further to my recent post on not understanding why physical length contraction in Lorentzian relativity doesn't imply an empirical difference with Einsteinian STR:

    It seems to me that Bell's theorem and the Aspect EPR-style experiments demonstrating non-locality in quantum mechanics imply an absolute simultaneity and therefore that there must be a preferred frame. The experimentally confirmed instantaneous action at a distance cannot occur otherwise (the actual results of the experiment would be observer dependent if there were no such frame).

    Hence (nutter alert) Einstein is wrong, not all frames are equivalent, and therefore we must look at a theory with an absolute space (hence my interest in Lorentzian relativity). This does not seem to be controversial to me, though I have hardly ever seen it mentioned by anyone?

    If you want to believe that nonlocality doesn't exist, then (it seems to me) you have only the following four options:

    (1) Loopholes: claim that improving detector efficiencies in the EPR-style experiments will invalidate the results. Usually taken to be desperate clutching-at-straws.

    (2) Deny `realism' i.e. the belief that there is a material world the description of which is the task of physics - but can this really be seriously questioned?

    (3) Believe the many-worlds interpretation, i.e. make two problems - nonlocality and macroscopic superpositions in measurement - go away, at the cost of believing in something apparently ludicrous (eight bazillion new universes per second). NOTE TO CONFUSED: Bell's theorem refers to correlations between the results of experiments in the two (widely-separated) arms of an EPR experiment. If every damned thing that could possibly happen happens at both ends and forms a separate universe then there are no such things as correlations therefore Bell's theorem is irrelevant.

    (4) Allow time travel into the past (barmy, unless one can demonstrate how or why this might happen).

    None of these things seem very plausible to me.

    So my question is the following. Given the fact that these experiments were done about a quarter of a century ago, and that to all intents and purposes nonlocality is an experimentally-proven fact, why has there been no wholesale switch away from Einsteinian every-frame-is-equivalent STR towards Lorentz style formulations? (note the same conclusions also apply to GTR as far as I can see).

    Cheers,
    Zenith
     
  2. jcsd
  3. Feb 14, 2009 #2
    Oh, it seems that way to you? Well perhaps, for the rest of us, you would propose an experiment that we could do to measure our velocity with respect to this absolute reference frame which you declare exists.
     
  4. Feb 15, 2009 #3
    Look, for anyone who thinks about it for more than two seconds, the fact that experimentally-demonstrated instantaneous action at a distance implies the existence of a preferred frame is not in doubt. It shows there to be an absolute simultaneity. This has been pointed out repeatedly in the literature, I think, starting with Bell himself.

    Given that Einsteinian STR denies the existence of such a frame, one could say that it has been experimentally determined to be incorrect (irrespective of whether you can determine your velocity with respect to this frame - which in fact you can't because of length contraction etc due to movement with respect to that frame in the Lorentzian relativity that we must now prefer).

    Note also that superluminal signalling of this nature violates causality - that is, gives rise to backwards-in-time signals in some frames - only if one assumes a local Minkowski structure for spacetime. Historically, the Minkowski structure was developed for a local physics. If Nature turns out to be nonlocal, then one should consider revising that structure.

    So your only real recourse is, as I said in the original post, is to choose one of my four reasons that nonlocality does not exist. Which do you prefer?

    Although one can't measure velocity with respect to absolute space, there are interesting proposals in the QM hidden-variables literature for instantaneous signalling at a distance. Normally this is screened out by the probabilistic nature of the results i.e one can induce correlations between particles in the two wings of an EPR experiment but over repeated trials the correlations will average out.

    Consider then a hidden variables interpretation such as de Broglie-Bohm pilot wave theory: here the only difference with respect to standard QM is that the wave function squared \Psi(x)^2 represents the probability that particles are at position x, rather than the probability that they are found at x in a suitable measurement. One then has the possibility of `non-equilibrium matter' where prob does not equal \Psi^2 - then all sorts of interesting things become possible, including instantaneous signalling. That would explain for example the `homogeneous universe' problem where parts of the universe always out of speed of light contact look the same - you would particularly expect to get 'non-equilibrium matter' in the early universe not long after the Big Bang.

    But that's by the way. Perhaps you could explain to me why instantaneous action at a distance does not imply a preferred frame?

    Cheers,
    Zenith
     
    Last edited: Feb 15, 2009
  5. Feb 15, 2009 #4
    GR does not deny the existence of an absolute reference frame (that's Occam's razor), it just isn't necessary to it (so forget about falsifying relativity so simply).

    While separated measurements are correlated in QM, every specific proposal so far (and there have been many here, so I'm placing the onus on you) for superluminal messaging has been shown to correspond to mere misunderstandings of QM. (Not to mention that it is the combination of relativity into QM that corresponds with our best verified predictions.) Contrary to your assertion, no QM experiment gives any evidence that any absolute frame exists.
     
  6. Feb 15, 2009 #5

    You're not getting my point. The mere existence of an infinite velocity entails the existence of an absolute simultaneity and thereby of an absolute space. Whether or not an infinite velocity can be attained in the transmission of signals is irrelevant for this argument: the one inertial system for which Einsteinian simultaneity coincides with absolute simultaneity would be the system at absolute rest - whether or not this system of absolute rest can be experimentally identified.

    And as for GR, do you really think that instantaneous, non-local, spacelike, universe-wide relations of absolute simultaneity (and EPR causal correlations) are logically, mathematically and ontologically consistent with Einstein's GR? Really?

    Your statement about 'it just isn't necessary' is simply an assertion of logical positivism - an idea discredited in philosophy since the 1960s - and of no relevance to the argument. It is also not true - which is what I'm trying to point out.

    Anyway - though it isn't really relevant - I've told you how to transmit superluminally: find non-equilibrium matter (in the hidden-variables sense, and I'm aware this isn't easy) - and then it follows straight off (proof widely available in the literature - I could direct you to specific references if you're interested). If you're stating that's based on a misunderstanding of QM, I'd love to hear why. If you wish to contradict this, then it seems to me your only recourse is to demonstrate that e.g. hidden-variables theories along de Broglie-Bohm lines are impossible. They've been trying to do that since 1927 - and are unlikely to succeed, since the only difference between that and standard QM is in the meaning of a single word - no extra mathematics at all.

    Thanks for showing an interest in this - but I haven't heard an argument from you yet that is anything other than a vague assertion of authority.

    Zenith
     
  7. Feb 15, 2009 #6
    Hello zenith8

    Quote:-
    -----It seems to me that Bell's theorem and the Aspect EPR-style experiments demonstrating non-locality in quantum mechanics imply an absolute simultaneity and therefore that there must be a preferred frame.-----

    As a beginner/layman i am puzzled by the statement about preferred frames. Before SR it was believed that light speed was infinite. You say that instantaneous action at a distance, which i assume means infinite signal velocity, leads to a preferred frame. But does this belief in infinite signal/light speed not bring us back to a pre-relativity/pre Einstein world view. This world view did not demand a preferred frame. Motion was still relative.

    Perhaps you could clear up this point as i may be making incorrect assumtions as to your meaning of preferred frame.

    Matheinste
     
  8. Feb 15, 2009 #7

    Hi Matheinste,

    Sure.

    Before SR it was not believed light speed was infinite as you state (the Greeks and the Arabs were talking about the finite speed of light thousands of years ago. Galileo proposed experiments to measure it using lantern shutters on different mountains, and Romer actually did measure it in I believe the 1670s - and got it more or less right.)

    Newtonian space is absolute in the sense that it is distinct from the relatively moving spaces associated with inertial frames, and also because the simultaneity of two events requires only a two-place relation of simultaneous with between events 1 and 2 rather than a three place relation between event 1, event 2 and a reference frame.

    Relativity already governed Newtonian mechanics i.e. it was impossible for an observer associated with an inertial frame to perform mechanical experiments which show whether he was at motion or at rest. Newton's laws of motion and gravity theory applied strictly only to the frame of absolute space or to inertial frames at rest with respect to absolute space, but they could be transformed and experssed in any sensible and apparent inertial frame (via a Galilean transformation i.e. adding velocities).

    Then when electromagnetism was invented in the 1860s it was realized that it wasn't relativized in the Galilean sense. It implied that electromagnetic waves propagate through an 'ether' (conceived of as at rest with respect to absolute space) at constant speed c which was independent of the motion of the wave source. So one would think you can measure speed at which waves in ether pass your measuring apparatus i.e. you can do what you could not do in mechanics: determine the speed of your inertial frame relative to absolute space.

    When Michelson-Morley failed to detect this motion (of the Earth through the ether), Fitzgerald, Lorentz and others tried to explain this result in terms of objects being physically squashed as they moved through the ether (leading to concepts of length contraction/time dilation as deduced by playing with Maxwell's equations). Mathematically this was essentially equivalent to what came later.

    Roughly speaking what Einstein did (apart from stating the matter more clearly) was to take the Lorentzian relativity above and say "since you can't detect the preferred frame, we might as well say it doesn't exist" and all frames are equivalent. Hence (eventually) Minkowski spacetime. Einstein did this because of the prevailing (but now discredited) philosophy of science at the time : logical positivism (i.e. science is only about stuff you can measure). Quantum mechanics suffered greatly from this as well.

    What the nonlocality experiments are pointing out is that there is a preferred frame. These are instantaneous interactions across any distance you like. If you state that something real exists (be it a particle, wave, both, or something else) which it is the object of physics to describe, then either the history as a matter of fact, or the final outcome as a matter of fact, would depend what frame an observer was in. In Minkowski spacetime, where every frame is equivalent you would get backwards in time causation. The only way out of this - as far as I can see - are the four ludicrous options I gave in my original post.

    So I'm saying that nonlocality is effectively telling us to go back to the pre-Einstein Lorentzian relativity. This is normally judged to be completely empirically equivalent to Einstein but with a different ontology (things really are physically squashed, as opposed to length contraction being a perspective effect).

    Hope that helps,
    Zenith.
     
    Last edited: Feb 15, 2009
  9. Feb 15, 2009 #8
    Hello zenith8

    Thanks for pointing out my mistake about the belief that light speed was infinite. You understand that the point i was trying to make was that even with absolute time there is no preferred frame as motion is still relative. So i am saying not that i disbelieve that non locality/ infinite transmission speed implies a preferred frame, its just that i don't understand how it implies this. Perhaps our definitions of preferred frame differs. To me a preferred frame is one that is special or unique in nature and not just preferred in the sense of one chosen to suit our purposes or ease our calculations. I am not implying that you think that either of these are what is meant but it would help me understand your point of view if i knew what your definition of preferred frame is.

    Matheinste.
     
  10. Feb 15, 2009 #9

    Fredrik

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    1. Completely out of the question. This would be like saying that more accurate measurements might reveal that if you drop a banana, it won't fall towards the ground.

    2. The implication isn't that the universe isn't realistic. It's that QM mechanics isn't. It's not inconceivable that we will someday find a better theory that is realistic. This of course requires that there's a way to exploit the loopholes in the arguments against hidden variables. See e.g. this and other articles by t'Hooft. Another possibility is that there's a way to describe exactly what the universe is like, but no way to use that description to predict the probabilities of the possible results of (a large enough range of) experiments. (E.g. if the description includes many (sub)universes, but doesn't tell us which one we live in). If that's the case, then the exact description of the universe doesn't meet the requirements of a scientific theory, and the implication is that science can't tell us what the world is really like. We might not like that, but the universe doesn't care about what we like.

    3. The MWI doesn't actually say that the number of worlds is increasing. (Theories of inflation on the other hand...but that's another story). I have other issues with the MWI though. In particular, I don't think anyone can point to a well-defined set of statements that actually defines the MWI.

    4. The EPR effect can't be used to send messages into the past, because there's no transfer of information from either of the measurement events to the other.

    Because FTL signals that contain no information can't cause any paradoxes.

    If you want to pursue this part of the discussion, you have to give an exact reference.

    Wrong. FTL "signals" of this nature don't violate causality because they contain no information. (The correct statement is that an FTL signal that contains at least one bit of information violates causality unless the time required for emission/detection grows at least linearly with the distance the signal travels)

    Wrong. The existence of an invariant infinite velocity implies the existence of an absolute frame, but no experiments indicate that this velocity is invariant (i.e. the same in all inertial frames).
     
    Last edited: Feb 15, 2009
  11. Feb 15, 2009 #10

    Dale

    Staff: Mentor

    In fact, there can only be one invariant velocity and experiments indicate that it is c. Therefore experimental results assert quite clearly that an infinite velocity is not invariant.
     
  12. Feb 15, 2009 #11

    Mentz114

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    I'm not convinced that the first sentence is correct. Since distance is irrelevant, the background could be described in any way you liked.

    Your whole argument depends on the proposition that instantaneous transmission is not possible if there's no absolute frame ( preferred ) frame. Now demonstrate it logically.
     
    Last edited: Feb 15, 2009
  13. Feb 15, 2009 #12
    Hi,

    Sorry for the delay - I was away from the computer.

    OK - let all particles in the universe be entangled i.e. the wave function of the universe cannot be factorized into products of functions which each depend only on subsets of the particle. This is not true, but that doesn't affect the argument. Then if I kick any one particle, every other particle in the universe will respond immediately irrespective of its velocity. This is because the wave function lives in configuration space i.e. it is a function which depends on all particle positions - an abstraction which combines or binds distant particles into a single irreducible reality. It defines an absolute simultaneity.

    The only inertial system for which Einsteinian simultaneity coincides with the above absolute simultaneity would be the system at absolute rest. If you continue to insist that all frames are equivalent, then you find that the history of the universe depends on the viewpoint of the observer. Hmmm.. Hence the requirement for Lorentzian relativity where such a frame does indeed exist, and you can describe the behaviour of moving frames with Lorentz transformed variables.

    You say you want a 'preferred frame .. that is special or unique in nature and not just preferred in the sense of one chosen to suit our purposes or ease our calculations'. Why is the above not what you want?

    Zenith
     
    Last edited: Feb 15, 2009
  14. Feb 15, 2009 #13
    See my last reply to Matheinste.

    Zenith
     
  15. Feb 15, 2009 #14
    Hello zenith8

    Quote:-
    ----You say you want a 'preferred frame is one that is special or unique in nature and not just preferred in the sense of one chosen to suit our purposes or ease our calculations'. Why is the above not what you want?----

    I do not "want" anything in particular i was just asking for your definition of a preferred frame. When you start talking about the wave function of the universe its all magic to me and seems a bit over the top. I don't understand it and if i need to learn about it to follow Lorentzian relativity i'm afraid i really don't have the time. So i will drop out of the discussion none the wiser.

    Matheinste
     
  16. Feb 15, 2009 #15

    Hi, OK - as you wish. But my definition of a preferred frame is above, as you asked.

    The wave function of the universe is a perfectly standard concept in quantum mechanics, and is neither magic nor over the top. Nothing to do with Lorentzian relativity as such.

    And you don't need to talk about the wave function of the universe if you don't want to - I was just trying to make the point with a big example. Any entangled wave function of a subsystem will do.

    Zenith
     
  17. Feb 15, 2009 #16
    Hello zenith8

    By magic i merely meant beyond my understanding. Is it not possible to give an explanation of your definition of a preferred frame without reference to quantum theory? I believe Lorentzian relativity does predate the advent of quantum mechanics.

    Matheinste
     
  18. Feb 15, 2009 #17

    Mentz114

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    By the 'the system' you mean the universe, because you started with the wave equation of the universe. In what sense can the whole universe be 'at absolute rest' ?
    Surely to speak of the universe being 'at rest' or 'in motion' is ... an oxymoron * ?


    * A figure of speech in which two words of opposing meanings are used together to express two contrasting qualities in one concept; A contradiction ...
     
  19. Feb 15, 2009 #18
    Hmmm.. OK, from the beginning.

    The nonlocality experiments define a universe-wide absolute simultaneity.

    Absolute simultaneity defines a global absolute separation of past and future, and thus we have a cosmological basis for a universal measure of time.

    This is clearly identical to the immutable, external, unobservable, unique time of Newtonian mechanics.

    By defining a universal time, we have a unique foliation of spacetime, and thus a unique space and we say this is an absolute space.

    To answer your specific question, we say this is an absolute space for substantival not relational reasons. Whatever is at rest in this frame obeys the unmodified Maxwell equations. In the rest frame, whatever is at rest in the absolute rest frame denoted by x,y,z in Maxwell's equations is at rest relative to absolute space.

    The absolute rest space (as distinct from the many 'relative rest' positions) is where spatial and temporal coordinates measure the real (not merely apparent) spatial and temporal values. If the universe is not at rest in this frame, then so much the worse for the universe.

    My main point, then, is that Bell's EPR correlations occur at the absolute time t and so it then seems to me to be difficult, in any theory, to try and admit an absolute time but adopt a relational theory of space as in Einsteinian STR..

    Is this not even a small prick* in your argument?

    Zenith

    * a sharp pain caused by or as if by being pricked.
     
  20. Feb 15, 2009 #19
    Hello zenith.

    But all you have done is take us back to an absolute space and an absolute time, with the universe at rest relatiive to itself. We've been there before. Where does that get us.

    Matheinste.
     
  21. Feb 15, 2009 #20
    Well, I've taken us back to absolute space and absolute time based on experimental evidence.

    That get's us to Lorentzian relativity (which is hardly used at present) and away from Einsteinian relativity (used by everyone at present, but which states that all frames are equivalent and is therefore incorrect, according to the above viewpoint). Such a view, if correct, has many important philosophical and possible practical implications.

    Like everyone else, I don't believe it can be that easy, but if not then I'm missing the flaw in the argument.

    Why doesn't nonlocality introduce a preferred foliation of spacetime?

    The answer must be either that nonlocality doesn't exist (but all reasons for thinking so seem not very plausible), quantum mechanics just doesn't describe reality correctly, or that the Einsteinian view of relativity is not correct.

    Zenith
     
    Last edited: Feb 15, 2009
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