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Bohm on von Neumann's measurement theory/
Stapp's response



From:

Reply-To: hpstapp@lbl.gov

To: Peter Mutnick

Subject: Re: Bohm on von Neumann's measurement theory, and a few other gems

Date: Thu, 1 Jun 2000 18:27:19 -0700 (PDT)

On Thu, 1 Jun 2000, Peter Mutnick wrote [quoting Bohm from "Quantum Theory"]:

"If for example... the brain contains essentially quantum-mechanical elements, then the point of distinction cannot be pushed as far as these elements. Even if the brain functions in a classically describable way, however, the point of distinction may cease to be arbitrary, because the response of the brain may not be in a simple one-to-one correspondence with the behavior of the object under investigation...

[Henry Stapp]

Exactly!

[Bohm, cont.]

"There is, however, a good reason to expect that the description in terms of the propagation of a signal which is in one-to-one correspondence with the behavior of the object eventually becomes inadequate.

[Henry]

Exactly!

[Bohm, cont.]

The reason is that nervous circuits in the brain frequently permit the feeding of impulses reaching a later point back into an earlier point. When this happens, it is no longer correct to say that the role of a given nerve is only to carry signals from outside, because each nerve may then be mixing in an inextricable (and nonlinear) way the effects of signals coming from other parts of the brain as well as from outside. When this stage is reached, the analysis in terms of a division between two distinct systems, i.e., the observer and the rest of the world, becomes inappropriate and, instead, it is probably better to say that all parts of the brain significantly coupled by feedback respond as a unit.

[Henry]

Respond as a unit! Exactly!

[Bohm, cont.]

It is this response as a unit that should probably be regarded as the process by which the observer becomes aware of the incoming signal.

[Henry]

Exactly! The Collapse is associated with awareness!

[Peter]

I'm not sure *this* is a "collapse" - I agree that it is an actual event nonlinearly bootstrapped to other elements of the brain by a THOUGHT. But, the collapse or reduction would seem to involve the further question of memory and an adequate template for the thought, i.e., the recording of the thought. The Everett issues might enter precisely here. Many (all conceivable) thoughts could arise at once (in the parallel processor of the quantum brain) with only one of them achieving the status of a recorded thought (making it through the von Neumann bottleneck).

[Bohm, cont.]

It therefore seems likely that the division between the observer and the rest of the world cannot be pushed arbitrarily far into the brain."

[Henry]

One must place the entire physical world inside the quantum world, and the abstract ego outside, ala von Neumann-Wigner, and continue to associate the collapse with awareness. This is the natural and rational placement.

[Peter]

Bohm's assumption was that at least part of the brain's functioning (the optical nerve, for instance) was classical. His assumption is then that one must retain a modicum of structure to achieve classical functioning (or quantum functioning on the other end). Hence, one cannot push the cut arbitrarily far in either direction. He also gives these other arguments about the re-emergence of quantum regions and the loss of one-to-one correspondence with the incoming signal due to feedback loops. It would seem that the optical nerve is classical by the natural placement of the cut, but not by the all-quantum placement of the cut, which is all-quantum solely due to the unavoidable feedback loops necessary to achieve the reduction.

But the point is that Bohm, as I think von Neumann, requires that there be some structure to the classical region that is distinct from the quantum region. You interpret abstract "ego" to be a thing without structure, much as mystics claim for the "Buddha Mind," or something of that sort, which they claim to exist but to not be analyzable into structure and function. That may be what von Neumann intended or it may not. Einstein (in the quote I gave) analyzes it a bit further by asserting that consciousness is the transcendental essence of the abstract "ego," which survives its demise, and then he also invokes the mystic shroud of unknowability by saying we can hardly imagine what consciousness is apart from its encasement in a body.

I think none of this is adequate, and I think what we need precisely is a detailed theory of the psychological and transcendental functioning of consciousness. For this we need to know the structure of the psyche, but the foundation for this has been laid by Freud, Jung, and others. From my experience of cosmic consciousness I have a detailed revelation of all this metaphysical structure and function.

Your above responses seem to me to require further elaboration. You agree with Bohm that the feedback loop within the brain, functioning as a unit, constitutes the awareness of the incoming signal, but then you assert that all of this is still quantum. Bohm assumes from practical considerations that at least the optical nerve is most certainly classical. But, putting that question aside, if the awareness has already been achieved by the feedback loop in the brain, which is entirely quantum, how can you demonstrate the role of the abstract "ego" in reducing the superposition? It seems you are further than ever from discovering the reduction process, because you have just postulated an existence that cannot be analyzed or understood in any way. You have brought about the reduction by fiat rather than by science.

All other forms of quantum theory at least hold out the possibility of further analysis of the the relations between the classical and quantum regions required for their ontologies. Bohr after 1935 clearly does this, Bohm in his 1951 book clearly does it, and even Everett does it by asserting that the reduction is now in the realm of the phenomenal experience of the actual observer - he does not preclude the further analysis of structure and function within that realm.

I view the abstract "ego" as many planes removed from the physical (six to be precise - physical, emotional, mental, etheric, phenomenal, causal, and meta-physical or classical, wherein dwells the abstract "ego"). The first three of these planes I regard as the expanded I, or actually observed system, the last three as the expanded III, or actual observer. The ether, perhaps related to the cosmological background radiation, I view as the prototypal measuring device, II, which is the medium and template for the registering of results.

I believe that in Bohm theory the only thing that is strictly speaking physical, from the nomological point of view, is the *observed position* of the particle. The rest is known theoretically, according to the equations and the structure of the theory, and one can plausibly claim that it is meta-physical. This is one meaning of the implicate order. From the ontological point of view, BTW, it is the wave function of the universe that is physical.

However, I do not think one can push the cut even as far as the entire physical world in nomological Bohm theory. This would be pushing it into the essentially quantum mechanical parts of the system, which Bohm says one cannot do. The reason is that in addition to the observed position of the particle, one must include the Bohm Point in configuration space as an essential part of the quantum system, yet this is not strictly speaking physical, since it is neither local nor observable. Nor does the Bohm Point in configuration space exhaust the description of the Bohm Particle, which has also a transcendental existence in the implicate order (the configuration space is an explicate structure, which has to do with the relative position of the particles rather than their essential nature - Heisenberg explains this difference very nicely).

There is the suggestion (not in Bohm's textbook, but later), that in addition to this natural placement of the cut, one can push the division all the way in either direction to get an all-classical or an all-quantum theory (these are presumably equivalent). Then, one must necessarily have a nonlinear quantum theory on the upper end, similar to de Broglie's or, better yet, Heisenberg's. On the lower end one has matter as a pure classical potentiality, which cannot be described *a priori* by a state vector formalism. The probability amplitude interpretation arises by deduction from the classical premises.

(Bohm's position on hidden variables.)

p. 623:

"We conclude then that no theory of mechanically determined hidden variables can lead to *all* of the results of the quantum theory. Such a mechanical theory might conceivably be so ingeniously framed that it would agree with quantum theory for a wide range of predicted experimental results. (We do not wish to imply here that anyone has ever produced a concrete and successful example of such a theory, but only state that such a theory is, as far as we know, conceivable.) But the hypothetical experiment suggested in Chap. 6, Sec. 11 would then be an example of a crucial test of the theory. If, in this experiment, we were able to violate the uncertainty principle, then the theory of mechanically determined underlying variables would be strongly indicated, whereas if we were not able to violate the uncertainty principle, we should obtain a fairly convincing proof that no correct mechanical theory could ever be found."

[Henry]

Bohm's hidden variable theory gives no empirical violation of the uncertainty principle. Whether one should call it "mechanical" can be debated: it seems pretty "mechanical" to me, apart from the manifest nonlocality. But I often demand locality in connection with "mechanical": then Bohm's HV theory would not be "mechanical".

[Peter]

As we discussed on the phone, his 1952 theory does not "lead to *all* the results of quantum theory," since it is limited to position measurements. One needs the further argument of John Bell that only those are essential. As we also discussed on the phone, the Bohm particle has a definite trajectory *in the holistic implicate order,* but in the local explicate order one must perform a position measurement to determine what trajectory the particle is in fact on. This should be, to achieve consistency, just the R^2 distribution law, but this is open to investigation. It seems that there is a bit of subtlety in measuring the position, which is a boundary condition, to determine the trajectory, for which the velocity is also a boundary condition. Are we regarding the R^2 distribution as the probability of finding the particle at the position or as the probability of the particle being on a certain trajectory and are these entirely equivalent?

Now, one would have to argue, to maintain the uncertainty principle, that the position measurement disturbed the guidance conditions (for velocity and acceleration), so that one could not presume that the particle would continue on the same trajectory it had been measured on. Presumably it takes some quantum of time for this disturbance to take effect, so that if one measures immediately, it will still be on the same trajectory (to match the results of quantum mechanics, such as the quantum zeno effect).

It seems to me that there is a rich field of investigation yet to be furrowed once one begins to take seriously what Bohm actually proposed, both nomologically and ontologically. Nor do I think it is essentially different or separate from the kinds of things you are proposing. I think Bohm was deep enough and sincere enough that any legitimate ontological theory will necessarily have to be integrated with his theory. In other words, he was working objectively, in a phenomenological sense, and his objective results cannot be ignored.

Ditto for Heisenberg's unified field theory. As we discussed, I don't see how one can have an ontological breakthrough without a fundamental theory. An effective field theory seems to be entirely compatible with a merely phenomenal level of interpretation. What I see as the hope for the future is the successful integration of Heisenberg's unified field theory and actual event interpretation, which Bohm agreed with, with Bohm's particle theory. Bohm's particle theory is essentially the structure of the vacuum and ground state with respect to Heisenberg's unified field theory. This is the missing element in Heisenberg's theory, the reason that they could never get it to work. In fact, it was technical considerations of how to treat the vacuum and the structure of the state space that presented insurmountable obstacles. In other words, they had no idea how to treat the particles ontologically, not just phenomenologically (as Platonic forms).



Peter Joseph Mutnick 1949 - 2000


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