Maxwell's equations and determinism

[reilly]

Actually what you measure are positions, energies, momenta. People use wavefunctions to calculate energies, and then measure energies, and the next thing you know they are saying they have measured a wavefunction.
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RA

Well, how else do you measure probabilities? (I'm aware of the convergence difficulties and other matters of mathematical rigor) When you have a coin toss, you measure which face of the coin is up. Then you count them. And, generally, you'll find, a 50-50 or close thereto, split. Of course, you want to make as many measurements as you can. As I'm sure you must know, physicists do a lot more with wave functions than calculate energy levels.

My thesis concerned electron-proton scattering, and I certainly used wavefunctions. When you do a scattering experiment you measure the probability that, say, an electron scattered from a proton, goes to a particular angular position. Sometimes you measure both electron and proton positions. But, in any event, you measure the modulus of the appropriate wave function. I don't expect you to believe me, but how about Bohm? He devotes over 70 pages to scattering theory in his classic book, Quantum Theory, and clearly demonstrates what I've just stated -- as do countless books and papers.


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C
All I am saying is that the complex-valued wavefunction is a hidden variable that is used to predict things that we actually measure, whereas Bohm's theory always speaks in terms of things we directly measure: positions, energies and statistical Hamilton-Jacobi functions. (How would a wavefunction be measured? With what sort of complex measuring device?)
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RA
Generally speaking the wave function is exactly that, one of space and time and spin and... If, in fact the wave function is a "hidden variable", in what space is this true? (Just to be precise, one normally does not consider a wave function as a variable.)

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C
My point about orbits was obviously a miss. I am not claiming that copernican/ptolemaic (Newtonian really) astronomy does not accurately predict the positions of celestial bodies. I was simply saying that the orbits we imagine the planets to move along cannot be directly observed.
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(RA) That's right for sure, certainly for complete orbits, or long sections thereof. It's not an issue of any consequence -- it well might be if our predictions of planetary motions were incorrect.
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C
Personally I don't give a crap about observation, but if someone attacks the causal (Bohmian) interpretation of QM on the grounds that quantum trajectories are inobservable (the "in principle" part comes from that unfounded assumption of QM that I brought up earlier), then I expect that person to think about which things we discuss in physics are truly observable: the truth is that many are not.

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RA
The fact that you speak so disparagingly of observations says, with all due respect, you don't know nuthin' about physics. Physics has been based on observation for many centuries. Without observations physics would be the nothing more than pure speculation, with no way to discern truth, just a time-killer for restless minds. -- barring a return to the divine right of kings.

I was interested in Bohm's ideas when I was a student, albeit many years ago. My professors kindly suggested to me that. if I wanted to be a professional -- which I did -- it would be wise to learn "mainstream" physics first, and then, if I felt the urge, to return to Bohm's work. Further, I sensed that many of my Profs had great respect for Bohm, as a very bright, able and accomplished physicist. I gave my students similar advice with respect to Bohm and the whole area of alternative interpretations of QM. In short, the standard track in any profession is: pay your dues, get your union card, start you career with some strength. (Bohm certainly did) --true for docs, lawyers, jazz musicians and blues singers, academics, .. Don't fall on your sword until there's a medic around.

And, my criticism of Bohm's hidden variables is that it has not produced any new physics, unique to its precepts. I know that many physicist have a similar position. Further, as I remember, computations are more difficult with Bohm's approach. Here's a challenge: compute the Lamb Shift for hydrogen a la Bohm's approach.
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C
Occam says that one should not increase, beyond what is necessary, the number of entities required to explain anything. Bohm's theory does not "increase the number of entities", it simply talks about a particle and a wave associated with the particle (the wave is a generalized Hamilton's statistical function).
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(RA)Strictly a matter of opinion.
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C
QM talks about both these things, but it speaks of the particle in a totally inconsistent nonsensical way (as if it teleports around through places it has "no probability of being". (RA-- How so?)

If the particle and its properties do not exist other then when they are measured, what sort of particle is that? Didn't someone accuse me of claiming the empire state building does not exist when we are not looking at it? How ironic that this is the world view of standard QM which I am against.

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The QM you discuss, and the QM I've known and worked with for many years appear to be rather different. Particles exist only when observed? (David Hume could make a case for that position.) Nope. Most of us do not believe that, as amatter of pragmatism. You totally misstate the "world view of standard QM", and vastly overstate the importance of the arguments about interpretation. Day-to-day physics works with a pragmatic Born-Bohr interpretation, and most physicists are involved in day-to-day. It's pretty basic to assume the real objective world exists. And day-to-day physics makes the same assumption.

I never got back to Bohm because I found high energy theory much more interesting and challenging. (But, of course, I will admit a bias toward observation, which might disqualify my intellectual seriousness.) What in the world do you mean by teleportation?

Why does QM upset you so much? The fact that we can participate in this forum is totally based on QM -- as in semiconductors,. Have you actually taken a graduate level QM course?
Are you aware that with the use of wave packets, trajectories can be defined loosely? -- a staple of formal scattering theory.

If you wish to cling to your ideas about QM, then if you want to be taken seriously, you will have to cite chapter and verse, rather than handwaving and indignation, about what you consider to be the inadequacies of QM, and give strong support based on observations and or mathematics. But if you really don't give a crap about observations, then as I said above, you are not doing nor talking about physics.

Regards,
Reilly Atkinson

PS By the way, Locrian, your definition of determinism is exactly the one used in physics. Philosophy might well talk a different talk.

 

[Juan R.]

Hi Crosson. You posted way back on page one:



I had always thought determinism stated that given the current universe state, there is only one future universe-state and it can be found. By found, I mean that with some method - maybe even utilizing tools we can only imagine - the future universe-state can be known.

Any comments on this?

Juan R. did extensive comments on why we cannot know that hypotetical future state in this thread, post ago.

 

[Juan R.]

Causal Determinism, as discussed by philosophers and myself, does not require there to be any method to determine the future universe state. For this reason, philosophers often avoid using the terms "predetermined" and "predestined", because these carry the connotation that somebody already knows the future U-state.

After the discovery of chaos in relatively simple nonlinear systems, it is generally agreed that humans will NEVER be able to predict the future U-state because our measurements only have finite precision, and we only have finite time to calculate. This does not rule out the idea that the universe is deterministic, as in Feynman's famous quote: "The universe integrates empirically", but it absolutely rules out our ability to make even short term weather predictions.

This is pure phylosophical speculation. You are asuming -phylosophically, of course- that universe is deterministic but you are not providing scientific evidence. Again your understanding of themes is -sorry to say this- superfitial. You are arguying just by the use of deterministic chaos. But what about nondeterministic chaos?

In nondeterministic chaos the initial state is perfectly stated and even if you know it exactly, and you compute with infinite precision, you cannot predict the future because Poincaré resonances break the unitary evolution and uncertainty arise. Of course, determinisitc chaos is valid in the limited regime when Poincaré resonances vanish, but is a approximation like the asumption T=0 in astronomy.

We could discuss about determinism from a phylosophical point of view but you appears confounded about the difference between phylosphy and science. There is no room for determinism on science except like approximated description when random forces vanish.

What about experimental proofs that Bohm theory is not correct? You are not replied to this still.

 

[Juan R.]

The QM you discuss, and the QM I've known and worked with for many years appear to be rather different.

Excellent reply!

I also arrived to the conclusion that QM studied by Crosson is very different of studied by rest of academia.

Also the Bohm theory studied by Crosson is different. All people, claim that Bohm theory is a theory of hidden variables and QM is not, but Crosson had claimed the contrary, which is, at least for me, rather atonishing.

Note: Crosson also claimed that planetary orbits are unobserved sugesting that Solar System model is an astronomical analogous of Bohm microtheory. It appears that now has rectified in this point.

 

[Crosson]

Do you people arguing against me feel that QM is true description of reality? Or do you view it as a black box for getting answers, as say a chemist does?

Don't start bringing up semiconductors, we all know way that QM earns its keep. The real question is whether or not QM describes the way the universe works on a fundamental level. We are not talking about the "day to day" in this thread, or what makes for easy calculations, we are talking about determinism, and determinism ultimately depends on the true metaphysical nature of reality.

It was Juan R.'s statement that determinism had been ruled out, that motivated me to start posting in this thread. Based on this statement, it seems that Juan has faith that QM is a description of reality, rather then being a statistical theory that represents our ignorance of the what is actually going on down there. Indeed, the QM which we have all studied includes the following postulate:

"The wavefunction provides the most complete description of the system that is, in principle, possible."

Here is a quote from Peter Holland, at the University of Western England:

"We emphasize the speculative character of the completeness assumption. It is not forced upon us by experimental facts and the more detailed theory of individual processes (Bohmian Theory) that it forbids is not excluded by the generally agreed upon formalism. A difficulty with it (CP) is that it takes for granted that the formalism is essentially closed and unambiguous."

I am not in love with Bohmian theory in particular, but I do believe that the completeness postulate is false, and that Bohm's theory is a step in the right direction towards moving beyond this obstacle.

The funny thing about the completeness postulate is that it is completely against the spirit of physics; it essentially tells all future generations that the problem is solved and is not up for discussion. The completeness postulate was developed out of the Copenhagen interpretation, and I see it as an arrogant, unnecessary, and almost certainly false assumption that has been kept alive only by a religion-like mob mentality of faith in the Copenhagen Interpretation.

If the completeness postulate is not true, then QM is entirely irrelevant to discussions about determinism. (I hope you see why).

 

[Juan R.]

Do you people arguing against me feel that QM is true description of reality? Or do you view it as a black box for getting answers, as say a chemist does?

Don't start bringing up semiconductors, we all know way that QM earns its keep. The real question is whether or not QM describes the way the universe works on a fundamental level. We are not talking about the "day to day" in this thread, or what makes for easy calculations, we are talking about determinism, and determinism ultimately depends on the true metaphysical nature of reality.

It was Juan R.'s statement that determinism had been ruled out, that motivated me to start posting in this thread. Based on this statement, it seems that Juan has faith that QM is a description of reality, rather then being a statistical theory that represents our ignorance of the what is actually going on down there. Indeed, the QM which we have all studied includes the following postulate:

"The wavefunction provides the most complete description of the system that is, in principle, possible."

Here is a quote from Peter Holland, at the University of Western England:

"We emphasize the speculative character of the completeness assumption. It is not forced upon us by experimental facts and the more detailed theory of individual processes (Bohmian Theory) that it forbids is not excluded by the generally agreed upon formalism. A difficulty with it (CP) is that it takes for granted that the formalism is essentially closed and unambiguous."

I am not in love with Bohmian theory in particular, but I do believe that the completeness postulate is false, and that Bohm's theory is a step in the right direction towards moving beyond this obstacle.

The funny thing about the completeness postulate is that it is completely against the spirit of physics; it essentially tells all future generations that the problem is solved and is not up for discussion. The completeness postulate was developed out of the Copenhagen interpretation, and I see it as an arrogant, unnecessary, and almost certainly false assumption that has been kept alive only by a religion-like mob mentality of faith in the Copenhagen Interpretation.

If the completeness postulate is not true, then QM is entirely irrelevant to discussions about determinism. (I hope you see why).

I respect philosophical opinions of people. I you want believe on determinism i see no problem, but you are doing an attempt to shown that physical world is deterministic, which, i already said, is impossible.

You incorrect statement begin with "is true description of reality?" You assumes what is reality and asumes what is true description. You assumes that world is deterministic and perfectly determined from positions of particles, but you are not showing that since you are beginning from that philosophical postulate. already explained becauses determinism is a phylosophical option but cannot be scientifically proven.

you cannot ask "The real question is whether or not QM describes the way the universe works on a fundamental level." If you do not know that mean fundamental level. QM says that fundamental level is QM says, and experiments prove this. Bohm theory claims an underlying deterministic structure that cannot be discovered/measured even in principle. This is reason that is called theory of hidden variables, but if those supposed variables are hidden and newer can be measured then Bohm theory is is in words of Pauli

artificial metaphysics.

we are talking about determinism, and determinism ultimately depends on the true metaphysical nature of reality.

But physics and science is about how world is in experiments/measurings, nor like the world can be imagined. I can imagine that quarks are composed of small pink elephants, but that is pure imagination, is not science.

It was Juan R.'s statement that determinism had been ruled out, that motivated me to start posting in this thread.

Exactly i said that i) determinism only was claimed by physics, newer was accepted in other complex sciences like chemistry or biology. ii) Determinism of Astronomy arises like approximation (already explain with equations) iii) nobody has proven that probabilities of QM are derived from a deterministic structure (in fact no one Bohm simphatizer has proved this still).

Based on this statement, it seems that Juan has faith that QM is a description of reality, rather then being a statistical theory that represents our ignorance of the what is actually going on down there.

No comment! I talked enough about this in this thread!

I newer said that QM was complete nor that wavefunction was a complete description of reality. In fact, it is well-known that |phy> is ONLY valid for pure quantum states. See also my words in the density matrix thread.

About the power of Bohm theory, even new versions of the theory are theoretically discredited and/or experimentally incorrect. I already said enough and add references on this.

In a recent "attack" (PHYSICS TODAY, March 1998) Bohmian believers said that new studies on QM like decoherence or the Gell-Mann/Hartle decoherent histories formalism were proofs of validity of Bohm theory. Of course, this is a nonsense and celebrated physicists Gell-Mann, Hartle, and others wrote public responses on that.

Extract from nobel laureate Gell-Mann and highly respected quantum theorist

Sheldon Goldstein's two-part article contains much valuable material. Unfortunately, his discussion of consistent histories is, in certain respects, misleading; at the very least, it is out of date.

Emphasis is mine.

Also an important physicist like S. Weinberg has replied

http://www.mathematik.uni-muenchen.de/~bohmmech/BohmHome/weingold.htm

Dear Professor Goldstein...

You are pretty persuasive about Bohmism. Is there a succinct (emphasis on succinct) clear statement of Bohm's theory that I can read?"

That is, fram from philosophies and asumptions about like Nature would be. Bohm theory explains all of QM (including relativistic processes) and explain things that QM cannot?

Reply is no.

 

[reilly]

Crosson -- I totally fail to understand your ad hominum bon-mots. The most arrogant person I've ever encountered, happened when I was a graduate student, was J. Robert Oppenheimer, who also was the most charismatic and charming man. His level of charisma was astonishing, of people in my lifetime only FDR and Churchill could compete. My experience was one lecture, and watching him at a faculty get togther. He was quite gracious in public, whether talking about national scientific policy, or the intracacies of QED. But, I gather, he could be devastingly pointed in private. I suspect there is a lesson there to be learned.

Between your scatalogical rejection of observation, and your assertion that there's a party line to be adhered to, and that, somehow, transistors, and I presume, superconductors, lasers, radioactive ispotopes and beams for cancer treatment -- two in my familiy have been treated that way -- and on and on, are really of no great consequence to you, I find it quite legitimate to question, as Juan R. has your knowledge of science and physics. I've had a copy the "Festschrift" for Bohm in 1987, Quantum Implications: Essays in Honour of David Bohm" for a few years, and have studied quite a bit of it. And, I note that a high level of civility abounds in the book.

That brings questions: has anyone actually observed the trajectories, say in the two slit experiment? Are they observable? What is the advantage of using highly nonlinear equations -- the HJ equation with quantum potential, and the continuity equation?

My view, and that of many physicists is that a state vector is defined by a complete set of variables -- true in classical physics, and in many engineering disciplines. Subject to future change? Of course. But, so far, this rather global approach has worked wonderfully. If you can poke an empirical (Oops, sorry about that reference to observation.) hole in the concept, let us hear it. Otherwise, are you willing to lecture to the entire scientific community about the "system approach" and statements about the inadequacy of such a utilitarian approach to state description, acepted as widely as a Visa or MasterCard credit card -- maybe even more so.

Party line? Hardly. Turns out that physicists are highly independent, just ask their employers. Most of us accept QM, imperfect as it is, troubling at the margins as it is, because we are convinced that it's the best game in town. Your idea and our idea of science and physics clearly differ. We are pragmatic, plumbers, quick and dirty back-of-the envelope folks with dirty hands and opportunistic minds. As scientists, our collective work over the centuries have brought enormous benefits of mankind -- my oldest son, a cancer survivor will, as an attorney, testify to that statement. We fly in airplanes, listen to the the radio, we can eat food that was harvested months ago, we are, unfortunately, very good at developing weapons, computing ballistic trajectories, we use electricity, use refrigerators, use natural gas, and ... You are, of course, free to reject such matters with whatever handwaving you wish. But, most of us will pay no attention to such rejection. I'm sure that you can figure out why.

Science is what scientists do. Physics is what physicists do. The plain fact is, that we have a long way to go to begin to say that we truly understand reality. But we do have an approach that has served us well over the centuries, and there is no reason to change horses at the moment.

And do remember, that physics is one of the most enduring and successful of human enterprises. If we turn out to be wrong, we admit it, and keep going toward what we perceive to be the truth. We have been guided by our own criteria for centuries; one of the few human activities that can so claim. The party line, if you will, is the process, which is grounded in empiricism and observation.

If A and B present you with their asserted complete and true theories of reality, how would you choose between them?

Regards,
Reilly Atkinson

 

[Crosson]

Between your scatalogical rejection of observation, and your assertion that there's a party line to be adhered to, and that, somehow, transistors, and I presume, superconductors, lasers, radioactive ispotopes and beams for cancer treatment -- two in my familiy have been treated that way -- and on and on, are really of no great consequence to you, I find it quite legitimate to question, as Juan R. has your knowledge of science and physics.

Of no great consequence? I am talking about determinism, which is the subject of this thread. Transistors are irrelevant to me in this discussion because they pertain to engineering, which is an application of physics, and is very far removed from the true metaphysical nature of reality. . Reilly, you strike me as much more of an engineer then a physicist. I consider physicists to be people like Einstein, who would never set foot in a laboratory.

As for you questioning my knowledge of science and physics, I think it is funny. The way you muddle engineering and physics, in a philosophical discussion where only the most fundamental physics is relevant, does not tend to make me take you questioning my credibility seriously.

 

[Juan R.]

A correction. The

"That is, fram from philosophies and asumptions about like Nature would be. Bohm theory explains all of QM (including relativistic processes) and explain things that QM cannot?"

is my interpretation of Weinberg question. It would appear outside of quote box. However, i think that I interpreted correctly Weinberg question.

 

[reilly]

Of no great consequence? I am talking about determinism, which is the subject of this thread. Transistors are irrelevant to me in this discussion because they pertain to engineering, which is an application of physics, and is very far removed from the true metaphysical nature of reality. . Reilly, you strike me as much more of an engineer then a physicist. I consider physicists to be people like Einstein, who would never set foot in a laboratory.

As for you questioning my knowledge of science and physics, I think it is funny. The way you muddle engineering and physics, in a philosophical discussion where only the most fundamental physics is relevant, does not tend to make me take you questioning my credibility seriously.

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You have totally mischaracterized Einstein. In fact, he was, among other things a rather good engineer and experimentalist. How did you ever get the idea that he never set foot in a laboratory?

He wrote a paper in 1923 with Hans Muhsam on an experiment they did for determining the permeability of filters. He and Leo Szilard applied for eight patents in Germany, six in Great Britain, one in the US, one in Switzerland, and one in Holland; all but two in Britain were awarded -- these mostly dealt with the design of a "noiseless household refrigerator." He holds a patent with Rudolf Goldschmidt on a then new type of hearing aide. He worked on a way (1907) to build a device to amplify small voltage differences, apparently in his own little laboratory.

If you want to understand the real rather than the mythical Einstein read the biography of Einstein by Pais. I've only quoted examples from Pais' book; I've heard of work on torpedo design, but I can't immediately find a reference.

By the way, Einstein's practical side was and I presume still is well known in the physics community. I learned my General Relativity from Prof. M. Schiffer, one of Einstein's mathematicians, as well as wonderful tidbits about Einstein's practical nature and other aspects as well. (The course became the well known, text by Adler, Bazin, and Schiffer. ) It's pretty clear that you really don't know much about Einstein, per your comment about his eschewing laboratories. The historical record proves you to be quite incorrect.

All I will say is that in my younger days, I was indeed a theoretical physicist, and considered as such by my peers and students -- why, some even congratulated me on my work and considered it to be physics.

To characterize Einstein as somehow beyond practical experiments is totally incorrect, and does damage to his early work on Brownian Motion and the Photoelectric Effect. Read Pais, and get it right.

Regards,
Reilly Atkinson

(Note: the inventors of the transistor won Nobels in physics. You are gong to challenge their awards as misguided?)

 

[Juan R.]

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You have totally mischaracterized Einstein. In fact, he was, among other things a rather good engineer and experimentalist. How did you ever get the idea that he never set foot in a laboratory?

It is the myth of the theoretical physicist, who can discover world only via thinking without experiment (note this is also the claim of string theorists and after of more than 30 years still achieved exactly nothing even if they claim that computed BH entropy, and obtained graviton, etc. reality is very different).

Also is popular that Newton obtained gravitation laws from the falling of apple. But that is a myth, no real. Newton was a experimentalist (during 30 years!) and did experiments in densities of mass and with he learned here, after computed motion of some astros, etc.

 

[CJames]

Juan, I am suprised as to your opinion of string theory. I am a mere undergrad so bear with me. I am thinking of going into theoretical physics and wanted to study string theory. Is that a misguided attempt? I'm asking not because I think you're wrong but rather because I would like to know something about what I'm doing with my life.

As for determinism, I don't think the question at this point is so much whether or not the universe is deterministic, but more whether it is in principle possible to prove or disprove. Considering the heisenburg uncertainty principle, I just don't see how you could possibly demonstrate a particle behaving in a deterministic manner. That makes it unfalsifiable.

As for what is "really" happening, other than what we can measure it is all up to you. I prefer to think of "particles" as physical waves that contain 1 unit rather than as probability waves. But that's just an interpretation

 

[Juan R.]

Juan, I am suprised as to your opinion of string theory. I am a mere undergrad so bear with me. I am thinking of going into theoretical physics and wanted to study string theory. Is that a misguided attempt? I'm asking not because I think you're wrong but rather because I would like to know something about what I'm doing with my life.

you may got many sources of information and after take YOUR decision. If in some moment your initial decision turn wrong, then you may solve that. This is life

There is a thread about this in PF with many information: documents, quotes of specialists, beliefs, last string conference, etc.

https://www.physicsforums.com/showthread.php?t=89539