Wikipedia:Articles for deletion/Quantum theory

Quantum theory

The article's talk page

The article's talk page contains under Talk:Quantum theory#expert needed discussion of whether "quantum theory" or "quantum mechanics" is the more general category.

Reason for nomination

That discussion appears at this time to favor the view that QM is the name for the general theory, which makes a page with this title inappropriate.

David R. Ingham 23:54, 19 October 2006 (UTC)

There is no such consensus on the talk page. A suggestion on the talk page to merge with quantum mechanics was rejected with only one vote in favor. This AfD is raised in error and should be summarily dismissed. --Michael C. Price ^talk 05:51, 20 October 2006 (UTC)

I could have waited longer, but the discussion showed no sign of justifying the page. David R. Ingham 06:09, 20 October 2006 (UTC)

You should have waited longer. This AfD is in violation of the the guidelines which say that talk page resolution should be sought first. And, as I said, the merge vote went against any change. --Michael C. Price ^talk 06:28, 20 October 2006 (UTC)

Continuing discussion

Looking at a text book for guidance, I find in Bjorken and Drell (1965), chapter 11 (page 2 of the second volume):

Our approach is best illustrated by the electromagnetic field, The potentials A$\mu \$(x) satisfy the Maxwell wave equations and may be considered as describing a dynamical system with an infinite number of degrees of freedom. By this we mean that A$\mu \$(x) at each point of space may be considered an independent generalized coordinate. To make the transition from classical to quantum theory, we must, according to the general principles proclaimed in Chap. 1, elevate coordinates and their conjugate momenta to operators in the Hilbert space of possible physical states and impose quantum conditions upon them. This is the canonical quantization procedure. It is a straightforward extension to field functions, which obey differential wave equations derivable from a lagrangian, of the quantization procedure of non-reLativistic mechanics. When it is done, there emerges a particle interpretation of the electromagnetic field-in the sense of Bohr's principle of complementarity.

If photons emerge in such a natural way from the quantization of the Maxwell field, one is led to ask whether other particles whose existence is observed in nature are also related to force fields by the same quantization procedure. On this basis Yukawa predicted the existence of the $\pi \$ meson from knowledge of the existence of nuclear forces. Conversely, it is natural from this point of view to associate with each kind of observed particle in nature a field $\phi \$(x) which satisfies an assumed wave equation. A particle interpretation of the field $\phi \$(x) is then obtained when we carry through the canonical quantization program.

They find nothing revolutionary about this. It is just proceeding to fields, according to the standard methods of quantum mechanics. The first volume is called Relativistic Quantum Mechanics and the second Relativistic Quantum Fields, but there is no suggestion that these are distinct theories. David R. Ingham 01:16, 20 October 2006 (UTC)

Contrast this to Messiah's text (that might precede this in a curriculum) in which chapters are spent discussing the surprising and fundamental differences between QM and classical physics. David R. Ingham 06:05, 20 October 2006 (UTC)

This discussion should be taking place on the article's talk page. --Michael C. Price ^talk 06:29, 20 October 2006 (UTC)

Messiah makes the point that if electromagnetic fields were not quantized, they would allow measurements to violate the uncertainty principle, so the underlying physics of field theory was already present in early QM. QFT is an approach to making quantum mechanical calculations. David R. Ingham 14:46, 20 October 2006 (UTC)

And yet quantum field theory and quantum mechanics are taught in separate courses. I wonder why... :-) --Michael C. Price ^talk 14:52, 20 October 2006 (UTC)

Opinions

Hold on, PLEASE READ THIS!

Nobody is coming here to LEARN Quantum Theory. People just want to learn [u]about[/u] it! The history of it, or brief history of it. We just want to read and get a general idea of what it is. When I come to the page, and see all of this nonsense about it being deleted, I can't really learn ANYTHING about physics because I don't know if any of it is real or not, when MOST of it is! The person that made this page, never said that what they wrote down and reported here was the end all be all about this subject. Just RELAX! You are putting seeds of doubt in everyones head. That is wrong. Or maybe you are just upset and jealous that he/she got here first, and YOU wanted to do the physics page. Thats just great, "nerd fights". Just relax, and go watch some Star Trek TNG. I'll watch it with you. ;)

• Delete and replaceReplaced with disambiguation page brief historical account, etymology, and comment on current usage including Quantum mechanics, Quantum field theory, Quantum chemistry, etc. The current "quantum theory" page is not up to the standard of other Wikipedia physics pages (quantum gravity is "third quantized"?) and effort spent trying to fix it would be better spent on the topic pages themselves better than it used to be, IMHO, but may still not satisfy everyone. The disambiguation page will of course have to be patrolled to remove pseudoscience links as soon as they are added, but that's rather easier with a disambiguation page because legitimate edits to it will be infrequent. Cheers, Michael K. Edwards 06:33, 20 October 2006 (UTC) (edits Michael K. Edwards 02:50, 21 October 2006 (UTC))
  • Comment The term "third quantization" exists -- including its use at the physics e-archives e.g. arxiv.org/abs/gr-qc/0606021 arxiv.org/abs/gr-qc/9611057. Making it a pure disambiguation page is a good idea (in fact I raised this suggestion on the talk page shortly after its creation). --Michael C. Price ^talk 06:48, 20 October 2006 (UTC)
    • Have you read those papers? I find both of them quite incomprehensible in detail; neither is peer-reviewed (although that hardly means anything anymore); and they use "third quantization" in two different, equally nonsensical (in my book), ways. Ioannis Raptis has transcended mere manifolds and spends forty pages of verbiage (and precious few equations) quantizing something he calls "Abstract Differential Geometry - Vacuum Einstein Gravity". A. Zhuk, on the other hand, seems to think that solutions of the Wheeler-deWitt equation need quantizing, and writes: "Similar to the quantum scalar field theory in the curved space-time we can expect that the vacuum state in a third quantized theory is unstable and creation of particles (in our case, universes) from the initial vacuum state takes place." If you have some sort of insight into this and can demonstrate that they are one and the same, methinks it would be WP:OR. If not, you probably don't want to be using the phrase "third quantization". Michael K. Edwards 07:09, 20 October 2006 (UTC)
      • No I haven't read those papers :-), I just picked the first two that came up. There are others on the arxiv, have a look. My point was to demonstrate the term is in use. BTW google yields 11,400 web hits for the search string ("3rd quantized" OR "third quantized" OR "3rd quantization" OR "third quantization"). --Michael C. Price ^talk 07:35, 20 October 2006 (UTC)

• Comment. I am concerned that some of the definitions and used in this article are either entirely non-standard or else do not reflect universally-used physics terminology. It's not clear to me, really, that "quantum theory" has a precise and universally-understood meaning. Likewise I believe that QFT can (and is) described as "quantum mechanical," which would seem to negate the stated division between the two. This article needs to cite sources and clarify whether terms are universally used, if it is to exist at all in its present form. I'm not advocating a particular course of action yet, but this clearly requires discussion. -- SCZenz 06:40, 20 October 2006 (UTC)

• Keep This should be thrashed out on the talk page instead of a knee-jerk AfD. --Michael C. Price ^talk 06:48, 20 October 2006 (UTC)

• Keep The word "quantum mechanics" cannot be used to mean both the set of all theories and one of them. While useage seems inconsistent in various text books, wikipedia must make an editorial choice between the 2 possible meanings. Pcarbonn 07:05, 20 October 2006 (UTC)
  • Historically speaking (in my unqualified opinion), "quantum mechanics" is the class of rather ad-hoc semi-classical Hamiltonian-based techniques which preceded QED, and QFT as the term is now understood (action-principle-based gauge theories) was only one of many possible successors to quantum mechanics. Many alternatives were explored between about 1927 (when Pauli and Dirac started fitting spin and special relativity together and identifying the proper form of the electron current) and 1960 (when experimental confirmation of the Ahanarov-Bohm effect validated the gauge potential as a physical field). Bohr/Heisenberg/Schroedinger style quantum mechanics is still taught to undergraduates, not least because it provides some insight into atomic physics without the forbidding mathematical machinery of QFT; and a sort of hybrid QM-QFT semi-classical technique still has a lot of value in computational chemistry and plasma physics. Trying to cram all that into QFT, or vice versa, wouldn't work very well. Hence the need for a disambiguation page at quantum theory. Michael K. Edwards 07:54, 20 October 2006 (UTC)
  • I don't think editorial choice is acceptable. Wikipedia does not define words; if there are ambiguities in the definitions, we report them—anything else is original research. -- SCZenz 14:04, 20 October 2006 (UTC)

• Weak keep -- I'm very much in favour with keeping the lemma. Look, e.g. there's old quantum theory which definitively isn't quantum mechanics. But the current content of quantum theory looks rather weak. --Pjacobi 08:31, 20 October 2006 (UTC)

• CommentDoes that mean you just want to keep it until the end of the week?  :)--Isotope23 14:35, 20 October 2006 (UTC)
  • Comment corrected. Fuzzy orthography at work... --Pjacobi 14:56, 20 October 2006 (UTC)
• This AfD nomination was incomplete. It is listed now. DumbBOT 09:50, 20 October 2006 (UTC)

• Keep for now, as this appears to be a content dispute. Suggest interested parties open an RfC or RfM... Even if consensus was Quantum Theory = Quantum Mechanics, this should be a redirect, not deleted; and even the DAB suggestion above requires no deletion, simply a consensus on the talk page.--Isotope23 14:32, 20 October 2006 (UTC)
  • Comment. Precisely, the whole AfD is a mistake. --Michael C. Price ^talk 15:05, 20 October 2006 (UTC)
• Keep. Terminology creep often occurs over the course of time. We should not, on that account, favor the growth of imprecision in terminology and in thinking. P0M 14:46, 20 October 2006 (UTC)
• Keep but move to the more widespread Quantum physics. Gazpacho 17:30, 20 October 2006 (UTC)
• Move to Quantum physics, and keep redirect. I think this discussion makes it pretty clear that (as I was taught by a former regional chair of the American Physical Society / assistant editor of the American Journal of Physics) QT and QM are not the same. - Che Nuevara 19:17, 20 October 2006 (UTC)
• Comment: Is it too much to ask that people read the article and evaluate it against the standard of major physics topics in Wikipedia? Or that they check an actual encyclopedia for the historical usage of "quantum theory", "quantum mechanics", and "quantum field theory"? Not that encyclopedias always get it right, either; but "quantum theory" does not appear to have any value other than as an umbrella term when describing developments later than about 1927 (when the observation of electron diffraction validated de Broglie / Schroedinger / Heisenberg "quantum mechanics" over the original Planck / Bohr / Einstein ansatz in which only radiation was quantized). Michael K. Edwards 20:35, 20 October 2006 (UTC)
  1. "Is it too much to ask that people read the article" - Please assume good faith and give people the benefit of the doubt that, if they're voting, they have read the article. This comment sounds very derogatory and, in my opinion, inappropriate.
  2. "and evaluate it against the standard of major physics topics in Wikipedia?" - That isn't an issue for AfD. Poor writing or organization is not a reason to delete an article -- it is a reason to rewrite it, and those kind of issues do not belong on this forum but on the article's talk page.
  3. "Or that they check an actual encyclopedia for the historical usage of "quantum theory", "quantum mechanics", and "quantum field theory"?" - If we deleted things on the basis of "an actual encyclopedia", then we would be Britannica. We're not. This comment is not likely to gain favor with the Wikipedia community at large due to its apparent (whether you meant it this way or not) characterization of Wikipedia as "a not actual encyclopedia".
  4. ""quantum theory" does not appear to have any value other than as an umbrella term when describing developments later than about 1927" - That sounds like a useful value to me. - Che Nuevara 06:31, 21 October 2006 (UTC)
• Comment...I read the article and as I said above, this is a content issue. Even if this term is commonly used incorrectly it still should be a redirect or DAB with an explantion at the target (in case of a redirect), or on the DAB page outlining the historical and current misuse of the term. In any case, that is an editorial and content issue which should be discussed on the talk page & is not a reason for deletion. Particularly if there is inconsistency in relation to the usage of this term it would be valuable to document that, provided that inconsistancy is well sourced.--Isotope23 20:46, 20 October 2006 (UTC)

• keep as disambiguition overview, maybe new as Quantum Theories andrej.westermann 22:15, 20 October 2006 (UTC)
• Keep. This is not the place for this debate. It should be on the talk page and maybe at the WP Physics Project. --Bduke 23:35, 20 October 2006 (UTC)

• Speedy Keep This is a content dispute move it to the articles talk page. Whispering 23:58, 20 October 2006 (UTC)