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Relativity and Quantum Theory

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I started a new thread since this was off-topic in the TEW thread.

I thought Böhm's interpretation was completely non-relativistic.

Bohm's original theory was a replacement for standard NRQM, yes. But since then people have found ways to do for (allegedly) relativistic quantum theories (e.g., multi-particle Dirac theory, QFT) what Bohm did for NRQM. Some of the extensions are controversial and/or ongoing research programs, but still.

A signal, or information, does have a meaning independent of human interpretation. It's something that has a causal effect.

I can tell you're not really up on the literature on quantum foundations or Bell in particular. People seriously interested in these issues use "signal" as a term of art referring specifically to the human activity of signalling (transmitting "information"), which is not coextensive with causal influences. Sending a superluminal signal requires some underlying causal influences that propagate superluminally, but the latter is not a sufficient condition for the former. The relevant causation must, for example, be sufficiently "controllable" that humans can harness it for their desired purposes. This distinction is important, because all the theorems proving that "relativistic" quantum theories are consistent with relativity actually only prove that those theories don't support superluminal signaling -- *not* that the theories don't contain superluminal causation and not that they don't require extra-relativistic spacetime structure.

In response to my claim that (even) orthodox QM requires such extra spacetime structure, you asked:

How so?

The collapse postulate. When a measurement occurs anywhere, the wave function describing (previously-entangled) degrees of freedom anywhere else in the universe changes *instantaneously*. And of course "instantaneously" is not a relativistically invariant concept.

Once again, I'm not sure how this is. I'm only a student, but I've been familiar with quantum field theory for a while, but the axioms (with a few modifications to use the Heisenberg picture instead of the Schrödinger, and to account for the infinitely many degrees of freedom) have seemed to work just fine. Perfectly Minkowski spacetime and all.

It is made to look that way by the fact that all you are ever asked to calculate in QFT courses is matrix elements (so you can calculate scattering cross sections and whatnot). But if you actually step back and think about the story the theory is telling for the evolution of the physical world over time, and what happens when somebody somewhere makes a measurement, and how other things have to evolve subsequently, you'll realize that there's no relevant difference between QFT and NRQM. They both require a collapse postulate to get the right answers, and formulating that precisely requires some un-relativistic concept of a dynamically privileged space-like hypersurface.

I believe many world myself (just to say), but because it has wavefunction collapse as an emergent phenomenon rather than something fundamental. Seems more parsimonious. But it's just metaphysics, and is indistinguishable from Copenhagen empirically, so I don't really argue it. And I've never seen it as "necessary" to relativistic QM.

Wavefunction collapse doesn't "emerge" in MWI. Unless you put it back in by hand at the world-mind interface (i.e., unless you cheat).

In response to my claim that Bell's theorem is not actually premised on "hidden variables" (popular belief to the contrary notwithstanding), you wrote:

This isn't true.

That's not much of an argument, so in response I'll just say: "Yes, it is." And: maybe you should go read some of Bell's own papers. I'd recommend starting with "Bertlmann's socks and the nature of reality" (conveniently reprinted in the book "Speakable and Unspeakable"). It is a brilliant paper. Nothing in the secondary Bell literature (and certainly not whatever textbook you got your information from) comes anywhere close. Pay special attention to footnote 10, where Bell states clearly that his "own first paper on this subject [his 1964 paper that first presented what is now known as Bell's theorem] starts with a summary of the EPR argument from locality to determinstic hidden variables. But the commentators have almost universally reported that it begins with deterministic hidden variables."

In regard to Bohmian Mechanics you wrote:

It is speculative because it postulates the existence of things that we have no evidence for. There are particles and pilot waves, and they are separate things. And the particles have a well-defined classical trajectory. If this is true, there should exist an experiment that confirms the pilot wave theory and at the same time contradicts quantum mechanics on some scale.

Actually we do have evidence that there are particles (think: spots on detector screens or tracks in bubble chambers), and evidence that the motion of the particles is somehow guided by a wave (think: all the little spots make an interference pattern as they accumulate). And by the way, according to Bohm's theory, when you measure the position of a particle, what you "see" is the actual pre-measurement position of the particle. So people who think that these particle positions are somehow "hidden" or "metaphysical" or "unempirical" are just wrong. If anything, it's the wave function that has that status. But I don't see anybody complaining about the wave function in other theories. I don't know what you mean by the word "classical" in the middle sentence. Yes, particles in Bohm's theory follow trajectories. But they are certainly not the trajectories predicted by classical physics. As to the last sentence, it would be nice. But it's of course fallacious to say that, in a situation that two different theories make the same predictions, one of them should be considered "verified" when its predictions are borne out, while the other should be dismissed a priori simply for making the same (empirically verified) predictions. It would be just as valid to say that orthodox QM should be dismissed until or unless it makes some prediction that is different from the predictions of Bohm's theory. The point is, when two theories make the same predictions, and those predictions are correct, you can't cite experiment directly as favoring either one. You'll have to appeal to some other standards, e.g., clarity, seriousness, parsimony, etc. And if you do that, Bohm is going to win over orthodox QM hands down.

Anyway, if we're going to mix relativity with QM (which has been successfully done), I may as well throw in some relativistic jargon and metaphysics. Everything has to be described from an observer's point of view, an observer within the universe who obeys the laws of physics. We'll call this observer Mufasa, because I'm sick of Anne and Bob.

I strongly disagree with your whole approach here. It's fine to describe physical reality "from an observer's point of view" -- if you mean, for example, using some particular reference frame for defining coordinates and whatnot. But this is very different from giving up the whole attempt to describe physical reality and instead just tossing around symbols, one term from which eventually is supposed to correspond to some kind of subjective conscious experience for some particular subject.

Trying to talk about the actual events of both measurements as though from an omniscient observer whose observing powers violate relativity is meaningless, by contrast, since relativity and QM both teach us (albeit in different ways) that observers are bound to the laws of physics.

I think you misunderstand what relativity is all about. You seem to be confusing it with solipsism.

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Travis I was wondering if I could get you to comment on the assertions on Relativity and the "pseudo tensor" below?

edit:[i asked because your comments "Unless you put it back in by hand at the world-mind interface (i.e., unless you cheat" and "But this is very different from giving up the whole attempt to describe physical reality and instead just tossing around symbols, one term from which eventually is supposed to correspond to some kind of subjective conscious experience for some particular subject. " reminded me of the comments below on relativity. hope it isnt too off topic ]

According to Einstein, in his gravitational field, gravitational mass and inertial mass are equivalent, and also, in a sufficiently small region of his gravitational field his laws of Special Relativity must hold. Here is what Einstein himself expounded (see his book 'The Meaning of Relativity', Science Paperbacks and Methuen & Co. Ltd., 1967, pp. 56-57, which Einstein revised in 1954, the year before his death):

Let now K be an inertial system. Masses which are sufficiently far from each other and from other bodies are then, with respect to K, free from acceleration. We shall also refer these masses to a system of co-ordinates K', uniformly accelerated with respect to K. Relatively to K' all the masses have equal and parallel accelerations; with respect to K' they behave just as if a gravitational field were present and K' were unaccelerated. Overlooking for the present the question as to the 'cause' of such a gravitational field, which will occupy us later, there is nothing to prevent our conceiving this gravitational field as real, that is, the conception that K' is 'at rest' and a gravitational field is present we may consider as equivalent to the conception that only K is an 'allowable' system of co-ordinates and no gravitational field is present. The assumption of the complete physical equivalence of the systems of coordinates, K and K', we call the 'principle of equivalence'; this principle is evidently intimately connected with the law of the equality between the inert and the gravitational mass, and signifies an extension of the principle of relativity to co-ordinate systems which are in non-uniform motion relatively to each other. In fact, through this conception we arrive at the unity of the nature of inertia and gravitation. For, according to our way of looking at it, the same masses may appear to be either under the action of inertia alone (with respect to K) or under the combined action of inertia and gravitation (with respect to K').

Stated more exactly, there are finite regions, where, with respect to a suitably chosen space of reference, material particles move freely without acceleration, and in which the laws of special relativity, which have been developed above, hold with remarkable accuracy.

Now Einstein's field equations for the static vacuum gravitational field, i.e. Ric = 0, violate his 'Principle of Equivalence' because the equivalence of gravitational and inertial mass, and the laws of Special Relativity, cannot manifest in a spacetime which by definition contains no matter! QED. Clearly, Einstein's writing of Ric = 0 was a major blunder. Consequently, if his energy-momentum tensor is zero there is no Einstein gravitational field. Hence his field equations must take the following form:

Gij/k + Tij = 0, (subscripts) i,j = 0,1,2,3, k = constant,

wherein the Gij/k are the components of a gravitational energy tensor. Thus the total energy of the gravitational field is always zero; the Gij/k and Tij must vanish identically; there is no possibility for the localisation of gravitational energy (i.e. there is no possibility for Einstein's gravitational waves). Moreover, this means that Einstein's General Theory of Relativity violates the experimentally well established conservation of energy and momentum, so if the usual conservation of energy and momentum is valid (bearing in mind that there is no experimental evidence to refute it) then Einstein's General Theory of Relativity is invalid.

Also, Einstein, aware that his theory violated the usual conservation of energy and momentum, simply invented his pseudo-tensor to save it, and by which he and his followers claim that his gravitational energy can be localized. However, Einstein's pseudo-tensor is a meaningless concoction of mathematical symbols for the following reason - it implies the existence of a 1st-order intrinsic differential invariant which depends only upon the components of the metric tensor and their 1st-derivatives (to see this just contract his pseudo-tensor and apply Euler's theorem). But the pure mathematicians G. Ricci-Curbastro and T. Levi-Civita proved in 1900 that such invariants do not exist! So Einstein committed another major blunder when he invented his pseudo-tensor.

In addition, Einstein and his followers resort to linearisation of his field equations to localize his gravitational energy and to obtain a "Newtonian approximation". This too is nonsense, because linearisation implies the existence of a tensor which, except for the particular case of being precisely zero, does not otherwise exist, as proven by H. Weyl in 1944. So LIGO and its international counterparts such as the AIGO in Australia and VIRGO in Europe, are all destined to detect nothing; and the black hole is not predicted by General Relativity.

Go here for a proof that Einstein's pseudo-tensor violates pure mathematics:

http://www.ptep-online.com/index_files/2008/PP-12-11.PDF

And here:

www.sjcrothers.plasmaresources.com/Levi-Civita.pdf

Go here for H. Weyl's 1944 proof that linearization of Einstein's field equations is erroneous:

www.sjcrothers.plasmaresources.com/weyl-1.pdf

Time To Straighten Out "Spacetime"

It is also alleged by most astrophysicists and astronomers that spacetimes described by the field equations

Ric = λgij, (subscripts) i,j = 0,1,2,3

where λ is the 'cosmological constant', describe gravitational fields in the absence of matter; that the spacetimes are curved by themselves, without the causative influence of matter; in other words that a gravitational field can exist in the complete absence of matter as a causative agent. However, there is not a shred of physical evidence to suggest that a gravitational field can exist without a material cause.

Curiously, the astrophysical scientists allege on the one hand that although this expression contains no sources for the gravitational field, because the energy-momentum tensor is zero, on the other hand they also allege that Ric = 0 contains a source even though the energy-momentum tensor is zero there too. In the latter case the massive source is inserted post hoc into the solution, and hence inadmissible. Furthermore, according to Einstein, matter is the cause of the curvature of spacetime, i.e. of the gravitational field, and the causative matter must manifest mathematically in a non-zero energy-momentum tensor in his field equations.

The late theoretical physicist John A. Wheeler has reasserted Einstein's geometrodynamics thus, "Matter tells spacetime how to curve and spacetime tells matter how to move". The fact that Einstein's field equations violate the usual conservation of energy and momentum also means that Ric = λgij is a physically meaningless expression to begin with.

Can you provide a proof that Einstein's pseudo-tensor is not mathematical gibberish? Can you provide a proof that Einstein's field equations do not violate the usual conservation of energy and momentum? Can you provide or otherwise cite experimental evidence that a gravitational field can have no material cause?

Stephen J. Crothers.

Edited by Plasmatic

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Travis I was wondering if I could get you to comment on the assertions on Relativity and the "pseudo tensor" below?

Looks like the kind of trash I get in my mailbox at work every couple of weeks. And, no, I don't want to discuss it any further than that. (Because, you know, I'm part of the big conspiracy.)

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Looks like the kind of trash I get in my mailbox at work every couple of weeks. And, no, I don't want to discuss it any further than that. (Because, you know, I'm part of the big conspiracy.)

Thanks for your time.

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The collapse postulate. When a measurement occurs anywhere, the wave function describing (previously-entangled) degrees of freedom anywhere else in the universe changes *instantaneously*. And of course "instantaneously" is not a relativistically invariant concept.

. . .

It is made to look that way by the fact that all you are ever asked to calculate in QFT courses is matrix elements (so you can calculate scattering cross sections and whatnot). But if you actually step back and think about the story the theory is telling for the evolution of the physical world over time, and what happens when somebody somewhere makes a measurement, and how other things have to evolve subsequently, you'll realize that there's no relevant difference between QFT and NRQM. They both require a collapse postulate to get the right answers, and formulating that precisely requires some un-relativistic concept of a dynamically privileged space-like hypersurface.

I have stepped back and looked at the story, and I gave you my (rather messy and inarticulate) description of, which you dismissed as "solipsism". Which, from what I recall, is a philosophy that claims that only one consciousness exists and reality is its making. Not a philosophy that claims statements about reality must be made from the perspective of an observer, which exists in a universe bound by the laws of physics and must obey those laws like anything else.

Wavefunction collapse doesn't "emerge" in MWI. Unless you put it back in by hand at the world-mind interface (i.e., unless you cheat).

Yes, it does. If you were to measure the state of a particle, e.g. an electron's spin, your state would become entangled with its--you'd be in a superposition of having measured spin up and of having measured spin down. You only observe one of them; you're one of the basis states making up the superposition. One of the "many worlds", so to say, that make up the total state of the universe. The fact that the electron could've had the other spin is completely lost to you, so you observe the wavefunction as having "collapsed". That's how wavefunction collapse emerges.

Actually we do have evidence that there are particles (think: spots on detector screens or tracks in bubble chambers), and evidence that the motion of the particles is somehow guided by a wave (think: all the little spots make an interference pattern as they accumulate). And by the way, according to Bohm's theory, when you measure the position of a particle, what you "see" is the actual pre-measurement position of the particle. So people who think that these particle positions are somehow "hidden" or "metaphysical" or "unempirical" are just wrong. If anything, it's the wave function that has that status. But I don't see anybody complaining about the wave function in other theories. I don't know what you mean by the word "classical" in the middle sentence. Yes, particles in Bohm's theory follow trajectories. But they are certainly not the trajectories predicted by classical physics. As to the last sentence, it would be nice. But it's of course fallacious to say that, in a situation that two different theories make the same predictions, one of them should be considered "verified" when its predictions are borne out, while the other should be dismissed a priori simply for making the same (empirically verified) predictions. It would be just as valid to say that orthodox QM should be dismissed until or unless it makes some prediction that is different from the predictions of Bohm's theory. The point is, when two theories make the same predictions, and those predictions are correct, you can't cite experiment directly as favoring either one. You'll have to appeal to some other standards, e.g., clarity, seriousness, parsimony, etc. And if you do that, Bohm is going to win over orthodox QM hands down.

Quantum mechanics postulates the existence of something-or-other with both particle and wave behavior. It predicts that one gets random results from measurement that follow some probability distribution. Pilot wave theory postulates that the waves and particles are completely different things and that the particle has a trajectory in the classical sense (that is, you can (in principle, if not practice because of lack of precision) predict exactly where it is and what exactly its velocity/momentum is at any time with a set of 6 parameters (initial location and initial velocity) and the Hamiltonian; by the way, this is what I meant by "classical trajectory"). Therefore, pilot wave theory postulates the existence of more things than quantum mechanics does. If it's true, then there should be a way to empirically verify that these particles with well-defined, classical trajectories exist. It's not the job of "orthodox QM" to prove they don't exist.

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If you were to measure the state of a particle, e.g. an electron's spin, your state would become entangled with its--you'd be in a superposition of having measured spin up and of having measured spin down. You only observe one of them; you're one of the basis states making up the superposition. One of the "many worlds", so to say, that make up the total state of the universe. The fact that the electron could've had the other spin is completely lost to you, so you observe the wavefunction as having "collapsed". That's how wavefunction collapse emerges.

But look at what you're actually saying. The whole physical universe, including your body and brain, is in some massively complicated superposition of states, each of which (taken individually) corresponds to some one familiar/definite way the universe could be experienced. But, in fact, according to the theory, the world isn't that way at all. So how come we experience it to be in one of those familiar/definite configurations? How come we don't experience it as it actually is, namely, in a massively complicated entangled superposition? Because some kind of magic -- which I hold is tantamount to the collapse postulate -- is "put in by hand" (i.e., just arbitrarily asserted as a new postulate) at the physical-universe / mind boundary. Which by the way makes a hash of virtually every foundational principle in Objectivist epistemology and metaphysics (e.g., perceptual realism -- according to MWI every conscious experience anybody has ever had has been massively delusional, in the sense that its "report" about the state of the external physical world is totally false... We see a cat that's definitely dead or definitely alive, but *really* it's neither, etc.).

Quantum mechanics postulates the existence of something-or-other with both particle and wave behavior. It predicts that one gets random results from measurement that follow some probability distribution. Pilot wave theory postulates that the waves and particles are completely different things and that the particle has a trajectory in the classical sense (that is, you can (in principle, if not practice because of lack of precision) predict exactly where it is and what exactly its velocity/momentum is at any time with a set of 6 parameters (initial location and initial velocity) and the Hamiltonian; by the way, this is what I meant by "classical trajectory"). Therefore, pilot wave theory postulates the existence of more things than quantum mechanics does. If it's true, then there should be a way to empirically verify that these particles with well-defined, classical trajectories exist. It's not the job of "orthodox QM" to prove they don't exist.

If you want to honestly compare the parsimony of orthodox QM and Bohmian Mechanics, it's a mistake to just say "Bohm adds particles to the ontology, so it's needlessly cumbersome." Yes, Bohm posits both particles and a guiding wave (just the ordinary wave function, for the record). But because of what it "adds" to orthodox QM, it gets to subtract a bunch of stuff -- namely, all of the vague and inconsistent measurement axioms. That is, there is no "measurement problem" for Bohm's theory the way there is for orthodox QM, because, for Bohm, all physical processes are on the same footing -- there's no need to divide the world into subject and object, quantum and classical, speakable and unspeakable, measurements and non-measurements, etc. You have just one set of basic dynamical postulates which apply *all the time*, whether anybody is making a "measurement" or not.

Now I gather you won't be too impressed by that comparison because you don't want to advocate orthodox QM, you want to advocate MWI -- which is precisely orthodox QM but with all the measurement postulates subtracted out. And I grant that, if you got a coherent theory that way, it would indeed show that Bohmian Mechanics is not maximally parsimonious (which wouldn't be the end of the discussion, but it'd be something). But in fact you don't get a coherent theory that way. You get something that is, frankly, crazy and unscientific. And, anyway, you end up having to sneak the measurement axioms back in at the mind-matter interface -- which, as Bell once pointed out, is a very uncomfortable place to be doing physics.

You seem like a smart guy, and I can only assume you have some interest in Objectivism. So I really don't want this to become confrontational. But you seem to have accepted a lot of dubious ideas from your physics training. The antidote to that is reading Bell. Get a copy of "Speakable and Unspeakable" and start reading it. As I mentioned before, "Bertlmann's Socks" is a great place to start.

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But look at what you're actually saying. The whole physical universe, including your body and brain, is in some massively complicated superposition of states, each of which (taken individually) corresponds to some one familiar/definite way the universe could be experienced. But, in fact, according to the theory, the world isn't that way at all. So how come we experience it to be in one of those familiar/definite configurations? How come we don't experience it as it actually is, namely, in a massively complicated entangled superposition? Because some kind of magic -- which I hold is tantamount to the collapse postulate -- is "put in by hand" (i.e., just arbitrarily asserted as a new postulate) at the physical-universe / mind boundary. Which by the way makes a hash of virtually every foundational principle in Objectivist epistemology and metaphysics (e.g., perceptual realism -- according to MWI every conscious experience anybody has ever had has been massively delusional, in the sense that its "report" about the state of the external physical world is totally false... We see a cat that's definitely dead or definitely alive, but *really* it's neither, etc.).

It would depend on the way that consciousness/perception works. I don't think the mechanism is known, and I definitely don't know it. But we don't consciously perceive the cat as both dead and alive, only one or the other. In the same way that measurement devices geared towards measuring the position of a particle see it localized in space, and not having multiple localizations in space.

If you want to honestly compare the parsimony of orthodox QM and Bohmian Mechanics, it's a mistake to just say "Bohm adds particles to the ontology, so it's needlessly cumbersome." Yes, Bohm posits both particles and a guiding wave (just the ordinary wave function, for the record). But because of what it "adds" to orthodox QM, it gets to subtract a bunch of stuff -- namely, all of the vague and inconsistent measurement axioms. That is, there is no "measurement problem" for Bohm's theory the way there is for orthodox QM, because, for Bohm, all physical processes are on the same footing -- there's no need to divide the world into subject and object, quantum and classical, speakable and unspeakable, measurements and non-measurements, etc. You have just one set of basic dynamical postulates which apply *all the time*, whether anybody is making a "measurement" or not.

I'll give you the lack of measurement axioms adds parsimony. Apparently I wasn't considering that.

Now I gather you won't be too impressed by that comparison because you don't want to advocate orthodox QM, you want to advocate MWI -- which is precisely orthodox QM but with all the measurement postulates subtracted out. And I grant that, if you got a coherent theory that way, it would indeed show that Bohmian Mechanics is not maximally parsimonious (which wouldn't be the end of the discussion, but it'd be something). But in fact you don't get a coherent theory that way. You get something that is, frankly, crazy and unscientific. And, anyway, you end up having to sneak the measurement axioms back in at the mind-matter interface -- which, as Bell once pointed out, is a very uncomfortable place to be doing physics.

I don't really try to advocate many worlds, I just brought it up to say I actually believe it. When it gets to metaphysics, I'm not particularly good at it, and it far too often seems to be just playing around with words (less with this crowd than with "mainstream" philosophy), so I don't like to argue my ontology over other ontologies (especially since mine is considered rather fringe, and because I find it hard to convey verbally and have obviously accepted it because I have an unorthodox way of even thinking about things), though I do somehow end up doing it anyway.

You did make the point that Bohm subtracts off the measurement axioms, though, so I can't argue it's any less parsimonious. So I have no reason to argue against it, though I still would like to defend Copenhagen.

You seem like a smart guy, and I can only assume you have some interest in Objectivism. So I really don't want this to become confrontational. But you seem to have accepted a lot of dubious ideas from your physics training. The antidote to that is reading Bell. Get a copy of "Speakable and Unspeakable" and start reading it. As I mentioned before, "Bertlmann's Socks" is a great place to start.

I'll look into it, thanks for the recommendation.

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It would depend on the way that consciousness/perception works. I don't think the mechanism is known, and I definitely don't know it. But we don't consciously perceive the cat as both dead and alive, only one or the other. In the same way that measurement devices geared towards measuring the position of a particle see it localized in space, and not having multiple localizations in space.

Just one quick comment. There's a dangerous large-scale sort of circularity in the idea that the real external physical world is radically different than how it "appears" to us in consciousness. (Indeed, there are fatal philosophical mistakes built into even that way of talking about the relationship of consciousness to reality, but I want to leave those aside for now and just make a mostly-physics point.) What is the evidentiary chain that leads to MWI in the first place? Well, surely it goes through believing in Schroedinger's equation, which in turn was posited based on how certain famous experiments from the 1910s and 1920s came out. But if MWI is true, then none of those experiments actually had the outcomes we (or, rather, they, back then) erroneously took them to have, and so the whole epistemic motivation for the theory crumbles away. It's, in this sense, not exactly self-refuting, but self-undercutting in a pretty ominous way.

It's may also relevant to point out that people who think about these kinds of issues seriously concede that there are some pretty difficult problems like this for MWI -- but, they argue, it's still worth it to take the theory seriously because it's supposed to be the only possible way of saving fundamental relativity (in the face of Bell's theorem, etc.). So it is pretty important that MWI really cleanly allow relativity. But this also turns into a huge problem, since the theory doesn't even posit any kind of ordinary 3+1 dimensional world populated by physical objects. If all there is is the wave function, then the universe is (again contrary to our subjective conscious experiences) a space of some extraordinarily high dimension (roughly, the configuration space for all the particles in it, since that's the dimensionality of the space the wf lives in). But relativity was never supposed to be about anything like that. It's supposed to be about the structure of 3+1 spacetime and how certain relational properties transform between different reference frame in that spacetime. So it's pretty bizarre for MWI to claim to be *the* uniquely relativistic version of quantum theory, when, according to it, there isn't even such a thing as 3+1 spacetime, nor any physical matter in it.

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I'm not sure how spacetime doesn't exist with many worlds. You have physical matter which is described by the wave function and is parameterized by space and time. Basically, as you said, it'd be QM (or QFT) without measurement axioms. Perhaps you could explain?

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I'm not sure how spacetime doesn't exist with many worlds. You have physical matter which is described by the wave function and is parameterized by space and time. Basically, as you said, it'd be QM (or QFT) without measurement axioms. Perhaps you could explain?

Suppose the universe has one spatial dimension and there are only two particles in it. So you have a wave function that is a function of three variables -- x1, x2, and t. If you tell me that this wave function provides a complete description of physical reality, I can understand that by visualizing a field that spreads over two spatial dimensions and evolves in time. On the other hand, I do not know how I can understand that function of x1, x2, and t as describing two things that move and interact in a 1-D space. So if you are proposing that this function *is* a description of two things that move and interact in 1-D space, it's you who will have to explain it to me.

I hope it's obvious how this is the same as what's at issue here. I've just made the numbers smaller to make things simpler. The real version is like this: suppose there are N particles in the real 3-D universe. Then the wave function (ignoring spin and treating things as in NRQM purely for convenience) is a function of 3N "spatial" coordinates (and t). So, if you tell me that function provides your complete description of physical reality, I can only infer that you think physical reality has 3N spatial dimensions and there's some kind of field that lives in that space. I don't know how to get from that picture/ontology to anything remotely resembling the world I see when I open my eyes. So you'll have to explain how that works.

Note that this illuminates another important feature of Bohm's theory. There's no problem of "finding" the familiar world of perception in the ontology posited by the theory, because the theory posits particles that move and interact in 3D space -- so, for example, it's going to include cat-shaped constellations of particles, tree-shaped constellations of particles, a me-shaped constellation of particles, etc. Of course the motion of these particles is somehow choreographed by this mysterious object, the wave function, which lives... I'm not quite sure where. But you can at least postpone that puzzle (if it is one) for another day and not have to worry that your theory doesn't include cats and trees and me. Which I think we'd all agree would be a pretty serious worry for anyone who cares about empirical adequacy of theories.

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Actually, that's pretty easy. Spatial translation. If you translate space by an amount in one direction, then N of your 3N parameters will change by the same amount. There are translational and rotational symmetries between your 3N parameters that make them behave as N points in a 3D Euclidian space.

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Travis,

Everything I've read by you so far indicates a great deal of agreement between us. The conclusion of superliminal deterministic causation seems the most philosophically and scientifically sound with regards to EPRB-type experiments. All the other interpretations I know of either fall apart logically under real scrutiny. Measurement axioms, many worlds, etc. seem like a way to rationalize and blow off a thorough, critical analysis of the underlying physics.

Consider a "toy" EPR experiment in which Alice is at one end and Bob at the other. When the experiment is started a continuous rod extending from an equidistant machinery spins the rod. This machinery is different from the machinery we normally encounter. This machinery was not designed by Alice and Bob, and neither knows anything about how it works, only that it spins a rod which they can stick their arm out and "feel" or "detect". This is analogous to using a sample of cesium or some other material to produce "photons". We do not have full knowledge or understanding of the precise state and construction of the internal machinery of that which produces the photons/spins the rod. This is why we don't know the precise final state beforehand.

Bob wishes to know which way the rod is spinning, i.e. its angular momentum. He sticks his arm out, stopping it, and determines it's spinning "up" (p = +1). Alice instantly knows the other side was spinning "down" (p=-1) because the rod is continuous. A continuous entity is capable of being perfectly rigid, i.e. an action at one end is instantaneously "felt" at the other end. The classic example is a continuous rod from here to Andromeda, if one were to push it they could instantly influence a planet in Andromeda.

This is just a toy model, of course, but it captures the qualitative idea. The point is that a continuous intermediary is capable of "perfectly rigid" behavior, which allows superliminal causation without violating locality or causality. Perhaps this intermediary is perfectly "rigid" in one direction but flexible in another. Indeed, if light is a torsional/transverse mechanism along this medium then we see why its propagation is finite while the propagation of other causal influences does not have to be. Perhaps influences that are directed "straight" along this intermediary are superliminal because of its perfect rigidity in this direction, but influences that are transverse are limited by the fundamental transverse flexibility of the intermediary.

I also think terms like "signal" and "information" are abused and that many people do not know precisely, in essential language, what they're trying to say when they use them. In general signals, information, patterns, etc. are what we understand from something as humans, not a fundamental aspect of Nature. I think "information" is a bit abused in the mainstream literature especially in regards to "hologram" theories. In general reification of abstract concepts is an issue imho.

"Just one quick comment. There's a dangerous large-scale sort of circularity in the idea that the real external physical world is radically different than how it "appears" to us in consciousness. (Indeed, there are fatal philosophical mistakes built into even that way of talking about the relationship of consciousness to reality, but I want to leave those aside for now and just make a mostly-physics point.)" -- ttn

From what I've read and deduced, falling into this trap amounts to accepting (at least in part or in some form) a Kantian philosophy.

On GR and the pseudo tensor, from what I've learned formally and informally, the "search is still on" so to speak for finding a direct physical link between the pseudo tensor and existent(s). Crothers raises valid issues but none, I think, that the scientific community is not already generally aware of. Since this is also partly a rel thread, what do you think of GR's compatibility with Objectivism?

Also what do you think of alternative relativity theories (not just Lorentz's original formulation) that do not set a c "speed limit"? In particular I've read some fascinating new material in the area of special/uniform relativity:

http://www.amazon.com/Electromagnetic-Reta..._pr_product_top

If you haven't read it, I recommend it. Particularly the section where he analyzes, in detail, a few "toy clock" models composed of moving charges in various arrangements and deduces their associated relativistic equations via classical EM.

And Flandern, who unfortunately died recently, has done some significant work in this area. His significant role in implementing the GPS system places him in a unique position to comment on relativity:

http://www.metaresearch.org/cosmology/gravity/gps-twins.asp

http://www.metaresearch.org/cosmology/grav...speed_limit.asp

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Actually, that's pretty easy. Spatial translation. If you translate space by an amount in one direction, then N of your 3N parameters will change by the same amount. There are translational and rotational symmetries between your 3N parameters that make them behave as N points in a 3D Euclidian space.

I don't understand this at all. It seems like you're just positing that there are certain relations between the various parameters that the wave function depends on. Certainly you can't *derive* from the given function of x1 and x2, say, that "'if you translate space by an amount in one direction" both x1 and x2 "will change by the same amount." I frankly don't even know how to parse what that's supposed to mean. Why should x1 and x2 "change" *at all*? They aren't quantities that take on some one particular value; they are the variables that the wave function is a function *of*. (Maybe you meant that the wave function would remain invariant if a certain N of the 3N variables were increased by some constant amount?)

And even leaving that objection aside, your whole answer here begs the question. What do you mean by "Spatial translation"? If all you've got is a field living in some 3N dimensional space, you're not yet entitled to discuss "spatial translation" (referring implicitly to 3-space). You must first either *posit* 3-space as a new axiom for your theory, or show that it somehow emerges from or is already secretly embedded in your field on 3N-space. Sometimes people try to take this last route and argue that you can "read off" 3-space from the structure of the Hamiltonian (in particular the potential energy part, which typically has terms that depend on the 3-spatial separation between particles). But I've never found that at all convincing.

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Bertlmann's Socks is certainly the minimum required familiarity one should have before considering any opinion on the matter of EPR. As far as physicists who can explain things simply and plainly, it doesn't get much better than Bell.

I think the language upon which quantum tends to be predicated, the particle, has led to a lot of the pain in interpreting EPR type behavior. If no particle/entity is actually transferred from the source to the polarizers, but rather an action/signal along a 2 strand entwined intermediary, there is no problem with superliminal causation. Indeed the intermediary would look something like what's illustrated in this paper:

http://pages.unibas.ch/phys-meso/Research/...hysics_full.pdf

A torsional motion along this seems the most likely candidate for what we call "light". Again, if this intermediary is continuous there is no reason for actions at one end not to be felt at the other. There is simply no call for such "explanations" as MWI or Copenhagen.

The issue left is whether to believe the quantitative prediction of standard quantum, which compels us to accept that what happens at each detector is a causal influence on the other. If we believe it, then there must be interdependence between the two measurements "instantaneously". If we choose to disbelieve it we have to explain the empirical success of the mathematics. The latter is not completely lost, there have been notable deviations from the quantum mechanical correlation in certain experimental situations:

http://arxiv.org/abs/quant-ph/0607172

I couldn't hunt down the reference, but I also read a while back that deviations occurred when polarizers/detectors reach a certain degree of efficiency, which is difficult to explain.

Edited by altonhare

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