Talk:Bohm interpretation

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Contents 1 Old comments 2 Critcism ? Or ignorance 3 category change 4 Everett's criticism 5 Pseudoscience claim reverted and many-particle case modelled 6 Bell 7 Hidden variables merge 8 Everett's Criticism 9 Article Cleanup Co-Ordination Point 9.1 Discussion 10 Deleted "commentary" 11 Criticism section

[edit] Old comments

Excised text:

Although for a long time considered a pariah among mainstream quantum physicists, Bohmian interpretation of quantum mechanics has recently gained ground due to the unequivocal experiment that has resolved the controversy Copenhagen vs. Bohm interpretation. Reactions from the physics community are yet to be seen. The paper on crucial experiment corroborating Bohmian interpretation (or, more correctly, shaking the Copenhagen orthodoxy) can be seen at Los Alamos site: http://xxx.lanl.gov/abs/quant-ph/0310096 (one could also consider http://xxx.lanl.gov/abs/hep-th/0304105 )

The quant-ph paper is hardly a description of a crucial experiment shaking the Copenhagen orthodoxy. It is a theoretical study comparing one model of the two slit experiment with another. There are slight differences between the results, but that could easily be due to differences between the inexact models used in each case. They do not claim that the differences are physical, and the experimental data fits both models. The main point of their paper was a demonstration of non-locality in the Bohmian interpretation. -- Tim Starling 23:53, Dec 4, 2003 (UTC)

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Hmm...I'm not sure whether we're talking about the same thing. As I've read in the quant-ph article, the point is that non-locality is present even in the classical physics limit, ie. decoherence alone is not sufficient for explanation of quantum-classical "transitions", or "cuts" (in von Neumann's lingo). According to Copenhagen- there is not a single bit of quantum theory (ie. anything that characterizes QT as such) in the description of "classical world". And here, in Bohmian int.- it is.

Btw, as an aside: I'd say that the entire page on Bohmian int. is very poorly structured. Bohm's int. vs. Copenhagen (or quasi-Copenhagen as defined by Von Neumann and Dirac): ontological vs. epistemological; quantum potential/active information vs. ordinary wave-particle and probability waves; nonlocalicty vs. locality; wholeness vs. -I dont know how to call it: particulariness ?...is presented very poorly. In his posthumous book "The Undivided Universe", Bohm has (with Hiley, and, of course, in numerous previous papers) presented ellegant and complete description of the physical world. This description is in many aspects more satisfying than the prevailing one (and I'm not saying it's flawless or "perfect" since such notions are nonsensical). Just- the weigh of habit and pragmatism keeps people stuck to the old ways (they give good description- but so does Bohm). The only thing is that non-locality is almost "emotionally" unacceptable to the majority of working phsyicists. But- this is hardly an argument.

As I've said: this article "collapses" Copenhagen orthodoxy. And- the page on Bohmian int. really deserves (even without it) more. Now, he looks like some pop-guru, which is, probably, the perception of interested outsiders-but not the truth about a serious and testifiable physical theory.

Mir Harven

You've got to look closely at what they mean by the "classical limit". They don't mean using pre-quantum physics, like Zernicke decoherence or whatever. They just mean the probability density. See the paragraph under equation 14. They calculate this probability density using Bohmian mechanics, and observe that it is different to the probability density calculated using the standard decoherence picture. If you look at figures 1a, 2a, 2b and 2c, you see that the Bohmian mechanics result agrees with the standard result at the experimental scale. However I have to admit that I'm not familiar with Omnès' work. To me, the phrase "Omnès doubts that decoherence is the answer to loss of coherence" sounds like an oxymoron.

Please sign your entries with ~~~~, which is automatically converted to a name and a date. -- Tim Starling 01:40, Dec 7, 2003 (UTC)

Hmm...first, I apologize for a belated answer-I was lost in a maze of other, more mundane interests. But-are you sure you got their contention right ? I'll try to summarize what I've read from (and I hope not into) their article:

• their point is that Bohmian computation agrees with the experiment (addressed earlier, at the beginning of the "Results" chapter, just below eq. (14).). So, we must stress that it's the results of the experiment they're trying to explain, not just an exercise in one way of computation or another (or, more precisely, one formalism or another). To repeat: they try to reproduce the results of the experiment.

• they do it in two ways: Bohmian and "orthodox" (in a relaxed sense-but it is still orthodox; works by Zurek and others, i.e. references 2 and 3 in the article). Understandably, orthodox (or, better, ordinary) approach is within ordinary QM framework and doesnt employ specifically Bohmian concepts of quantum potential and active information. Just as an aside-one should mention that Bohmian approach is not new with regard to math formalism, but re interpretation of rather ordinary Sch. eq. (or, Ham.-Jac.), which simply gives a part Bohm had interpreted as quantum potential and developed a new view on QM with testifiable results. So, Bohm is (as anyone familiar with "The Undivided Universe" knows) not original re mathematical formalism (it's just a wave function in radial form, and Sch.eq. applied on it)-but in interpretation that denies central features of ordinary QM: no wave-particle dualism (electron is particle guided by quantum pot. field); no epistemological approach (i.e., quantum realism and ontology); and, most strikingly: non-locality vs. locality of ordinary QM (or any ordinary physical theory). Not to delve into intricacies further, what's at stake in this article is: there should be no non-locality in classical systems. And it is-according to the experiment and their Bohmian computation. But not in the ordinary decoherence framework. Look at this: "What it is remarkable is that this behavior even takes place in the case in which the coherence is completely lost (ô=0). This result is totally unexpected, and is due to the fact that the non–local behavior of quantum mechanics is preserved even in this case.This supports Omn`es’ suggestion that something else it is necessary, apart from decoherence, in order to make quantum mechanics exhibit a true classical behavior. In a Bohmian sense, even when interference e�ects are lost, still it is possible to distinguish between the result observed when the two slits are simultaneously opened, and those obtained from the sum of trajectories coming from each slit independently............

Conclusions. – By applying Bohmian mechanics to the paradigmatic two–slits experiment we have addressed a question raised by Omn`es about the possibility of decoherence theory to fully explain the appearance of classical behavior in a quantum system. Our results show that, although quantum statistics erases information about interference e�ects, there is still a strong non–local quantum correlation in the behavior of the system in the case of null coherence. This is due to non–locality in quantum mechanics, making that the probability density keeps information about the whole system. Such an information is “transmitted” to each particle, so that they “know” whether the other slit is open or not."

• or, in everyday speech: decoherence approach (i.e. ordinary QM) doesnt explain non-local behavior of classical systems (quot. "there is still a strong non–local quantum correlation in the behavior of the system in the case of null coherence.") This non-locality is the feature completely absent in ordinary QM, and peculiar to Bohmian mechanics. What needs to be stressed again: they point to the results of the experiments-not just their calculations. More simplistically: the keywords are CLASSICAL SYSTEM and NON-LOCAL BEHAVIOR (experimentally measured). And this is explained only (in this case) within the conceptual apparatus of Bohmian mechanics, and NOT decoherence.

• also- I do not see this corroborated by graphs, hence there is, IMO, discrepancy between their contentions and presented pictures.

Mir Harven 23:28, 13 Dec 2003 (UTC)

"It also differs in a few matters that are experimentally tested with no consensus whether the Copenhagen interpretation has been proven inadequate (and this inadequacy just glossed over due to inertia in physicist circles- not unlike the situation with cold fusion)" Excuse me, but isn't this a little bit biased of the author?

This page is a mess in explaining its subject. I edited it a little, tried to clarify. Still a mess, tho. 64.168.30.87 03:29, 24 Oct 2004 (UTC)

[edit] Critcism ? Or ignorance

Although personally I dont think Bohmian interpretation will bear much fruit-when criticised, it must be on fair basis. And, at least half of "criticisms" are, to put it mildly- lame. I've deleted, now, only the 1st point, since "inelegance" is personal preference, and, judging from the majority of opinion- this would be the last objection re Bohmian view. As for redundance-current physical theories are full of variables that are not directly verified and are props that may very well turn out to be just concoction: for instance, Higgs boson and dark matter. Other cristicism will be reviewed in due time, but, weaknesses of Bohm's interpretation cannot be addressed in such a manner, teeming with half-truths, since Copenhagen formulation abounds with even more "unacceptable" or concocted notions (anyone remember problems with classsical-quantum division, "healed" by Bohr's Correspondence pronciple-pure scholasticism, not provable at all). Bohm's "sin", if any, is that he was too timid and not radical enough. Mir Harven 12:57, 29 Oct 2004 (UTC)

[edit] category change

Linas removed this article from [Category:Quantum mechanics] and added [Category:Quantum measurement]. I reverted that edit, and then he reverted mine, with a note asking not to revert his change without discussion. OK, I'm here. Why did you remove this article from the Quantum mechanics category? --goethean 19:17, 14 May 2005 (UTC)

Yes, I'm puzzled myself. The articles under the rubric interpretation of quantum mechanics now fall under quantum measurement. Though not quite utterly absurd, this reclassification is quite idiosyncratic.--CSTAR

[edit] Everett's criticism

I've added Everett's critique of Bohmian mechanics:

The Bohm particle(s) are not observable entities in the sense that we can remove them from the theory and still account for our observations, since Bohm regards the universal wavefunction as a complex-valued but real field. This was first noted by Hugh Everett whilst developing his many worlds interpretation of quantum mechanics, who showed that the wavefunction alone is sufficient explanation for all our observations.

All it needs is for a response to be added, which I can't do myself since I don't know of a valid rebuttal. --Michael C Price 14:29, 16 June 2006 (UTC)

[edit] Pseudoscience claim reverted and many-particle case modelled

Unsourced and probably OR claims reverted; they seemed mainly to be aimed at the lack of a many-particle treatment which is now present. --Michael C. Price ^talk 02:01, 6 August 2006 (UTC)

[edit] Bell

There's a lot of stuff about Bell appearing that should really be in the Bell's theorem article. --Michael C. Price ^talk 23:32, 22 August 2006 (UTC)

I'm ging to delete it unless its presence is explained. --Michael C. Price ^talk 01:36, 24 August 2006 (UTC)

[edit] Hidden variables merge

Anyone object to merging Hidden variable theory into this article? It was what Bohm originally called his theory. --Michael C. Price ^talk 01:36, 24 August 2006 (UTC)

I see someone is of the opinion that this shouldn't be called "hidden variables" and has removed some references to the term. Well that's what Bohm called it originally -- and how it is often called -- so we should mention it, even if John Bell thought otherwise. --Michael C. Price ^talk 20:14, 26 August 2006 (UTC)

[edit] Everett's Criticism

The response to Everett's criticism looks like original research, with the claim that Everett's theory requires extra assumptions -- also such issues about other interpretations should really be dealt with on their respective talk pages (e.g. Talk:Many-worlds_interpretation) rather than here, so I propose we delete this claim.

Focusing on Bohm's theory and role of the particles, I don't think the response actually addresses the issue of the unobservability of other universes (empty parts of the universal wavefunction), although of course adherents of the various interpretations are never going to agree about this. Can we say that followers of Everett (who hold the non-collapsing wavefunction is sufficient to account for all observations) see the Bohm particles as superfluous, whilst others regard them as necessary to realise one possibility from amongst many? --Michael C. Price ^talk 21:21, 1 October 2006 (UTC)

The response is not original, just a brief summary of Bohm's own critique of MWI. See e.g. §13.6 of The Undivided Universe:

If we adopt DeWitt's approach, then, as we have seen, it is necessary to supplement this with some further principles involving an as yet unavailable definition of complexity and further equations determining just how this would determine the splitting of universes. On the other hand, if we adopt Everett's approach or indeed that of the many-minds interpretation, we have to do something similar with regard to the splitting of awareness. In this connection a complete and consistent expression of these interpretations would, as we have seen, require new principles and assumptions of a speculative nature going beyond our present knowledge of awareness and its possible relationship to Hilbert space. (p. 315)

Regarding how one possibility is realized from among many, it would be misleading to give the impression that one theory needs to explain this and the other doesn't. Both Everett and Bohm recognized that they have to explain it, they just did so in different ways. Everett used the splitting of universes (or awareness), so he didn't need the particles. Bohm used the particles, so he didn't need the splitting. Any comparison of the two theories ought to bring out this parallelism. —Were-Bunny 17:16, 9 October 2006 (UTC)

Thanks for supplying the Bohm quotation, this demonstrates that this particular claim about the necessity of particles is not original research -- what it doesn't show is that this is universally accepted, especially by adherents of other interpretions (as you would expect). Hence the qualifer "in Bohm's view" is required to WP:NPOV it. --Michael C. Price ^talk 00:01, 10 October 2006 (UTC)

Bohm's interpretation is not universally accepted, so it is highly unlikely that his views on this particular point (or any other point) of his interpretation are universally accepted. But that's irrelevant to the issue at hand, which is the question of how Bohm responded to Everett's criticism of the Bohm interpretation—i.e., a question about what Bohm thought, not aboout whethter others agree with him. If universal acceptance were the requirement for explaining the features of the Bohm interpretation, the whole page would have to be empty. Since The Undivided Universe is Bohm's most authoritative work on his interpretation, no further evidence of his views is needed here. Furthermore, the redundant qualifiers ("in Bohm's view," "Bohm maintained that," "in Bohm's view") also are not needed because the reader already knows that the whole page reflects Bohm's views, except where otherwise noted. A qualifier is needed only once following someone else's views, to alert the reader to the transition. —Were-Bunny 22:12, 10 October 2006 (UTC)

You misunderstand my point (or rather the Wikipedia guidelines). No one is saying that Bohm's views are inappropriate in the article -- but it must be made clear where they are Bohm's views and where they are views endorsed by the wider community. All statements in Wikipedia articles should be explicit about their sourcing if challenged; the qualifiers are not redundant, placing a single qualifier is not sufficient since this article (like others) contains statements which vary with their acceptance from statement to statement. --Michael C. Price ^talk 01:41, 11 October 2006 (UTC)

You are misapplying the Wikipedia guidelines in this case. This paragraph makes no mention of general opinion. It states that Everett made a criticism of the Bohm interpretation (e.g., that particles are not needed) and that Bohm responded to that criticism by explaining why they are needed. These are claims of fact, not opinion--i.e., the fact that Everett and Bohm did or did not make the respective statements. To verify the accuracy of these facts, all that is needed is to cite the appropriate writings of Everett and Bohm. Other people's acceptance doesn't matter because no claim is being made about whether the expressed views are generally accepted. If you think the paragraph makes some additional claim about general opinion, the burden is on you to point out specifically what it is. If there is such a claim, it should be clearly identified as such. At present it is not; all opinions are attributed to either Bohm or Everett. —Were-Bunny 20:01, 11 October 2006 (UTC)

I must have been unclear -- I have no problem with Everett's and Bohm's views being reported: it was those opinions that were not clearly attributed and that could be misinterpreted as general statements of scientific fact that concerned me. Best wishes, --Michael C. Price ^talk 20:10, 11 October 2006 (UTC)

You're being extremely vague and unclear. Please try to be much clearer. I've asked you to identify specifically which opinions you believe are not attributed to either Bohm or Everett. Please do so as clearly as possible. —Were-Bunny 16:46, 12 October 2006 (UTC)

I find your requirement rather odd. I have already corrected the article by adding the appropriate attributions, which you originally objcted to. So to be completely explicit: I am happy with the article as it is since the questionable statements (i.e. opinions) are appropiately attributed. --Michael C. Price ^talk 19:26, 12 October 2006 (UTC)

[edit] Article Cleanup Co-Ordination Point

Uhh, this request for cleanup is confusing and unclear. Is there some specific complaint? linas 04:39, 13 December 2006 (UTC)

Pockleanbot has been removed, so unless a real person has something to say, I'd say to ignore it. Fephisto 01:10, 14 December 2006 (UTC)

[edit] Deleted "commentary"

I have delete the section "commentary" for the following reasons.

1:It is unverified.

It make a number of claims about the beliefs and opinions of physicists which are unsubstantiated

2:It is PoV

A number of the claims and clearly biased, implying motives and the like

3:It is essentially a personal essay

Whilst fascinating, Wikipedia does not publish original thoughts and research.

Jefffire 11:35, 14 December 2006 (UTC)

[edit] Criticism section

I am not sure if Bohmian mechanics are just really insecure, but the `criticism' section truly is a fiasco. Surely there is some Wikipedia policy or guideline against having criticisms each followed immediately after with a `response'. In many cases, moreover, the `responses' have a whiff of original research, or at least original syntheses from existing literature, and many of them don't actually address the criticisms in any meaningful way (probably because no such way exists). I don't want to edit the article and disturb the equilibrium that tends to develop around these sorts of topics, but could a regular please try to sort this out? Rosenkreuz 08:50, 11 January 2007 (UTC)

The point of the criticism section is to inform the reader: this is what the critics say, and this is how the adherents defend their position. Whether the responses are adequate is left for the reader to judge. (I wrote one of the responses and I'm not a Bohmian.)--Michael C. Price ^talk 08:58, 11 January 2007 (UTC)

I understand as much. Only most similar articles don't have such `response' opportunities, I don't think...the reader judges the validity of the criticisms based on the content of the theory as discussed in the article itself, not on a list of possible fixes. Having such a list, moreover, invites an endless cycle of criticisms and counters, surely? It seems like a bit of a `POV-trap', to me, which is wide open to abuse. Rosenkreuz 09:07, 11 January 2007 (UTC)

Yes, but interpretations of quantum mechanics are a particularly controversial area, even amongst leading researchers who care to venture an opinion. Controversial topics often (but not always) have a criticism section. That's not POV abuse, provided all viewpoints get to be expressed (whether or not they are valid -- which Wikipedia has no opinion about, of course). Any controversial subject will attract an endless cycle of criticisms and counters -- the criticism section is an attempt to channel this more productively. --Michael C. Price ^talk 09:13, 11 January 2007 (UTC)

I know that. I don't object to a criticism section at all: that much is necessary. It is the responses which are misplaced, I think. For example, the article on the relative state idea contains an `acceptance and criticism' section — which is good — but it doesn't have a list of comebacks by the Everites to every point raised in objection to the theory — and nor should it. Why should the same rules not apply to the Bohm interpretation? Rosenkreuz 09:19, 11 January 2007 (UTC)

Hmmm.. Heh, I helped write the MWI criticism section. I guess that section has a more unified approach than here. I hesitate to remove the "response"s here because I'm sure someone will object. And I admit I'm too lazy to do the complete rewrite you seem to be suggesting. --Michael C. Price ^talk 09:26, 11 January 2007 (UTC)

A nonspecialist reader says: the criticism/response format is VERY helpful; please don't delete it. —The preceding unsigned comment was added by 72.70.250.127 (talk) 02:26, 2 April 2007 (UTC).