Talk:Matter wave/Archive 2

Incorrect Title
The title of this article should be "De Broglie wavelength." This concept is well-defined and is commonly used in physics. The phrase "matter wave" may be more appropriate for a "simple wiki" where all terms are dumbed down, but this is wrong for a regular encyclopedia. cecoppola — Preceding undated comment added 11:15, 13 September 2014 (UTC)
 * I agree in principle. But this article is about more than just the length of the wave, even if that has historically been the most important aspect. Perhaps "de Broglie wave" would be better. That page currently redirects here, while de Broglie wavelength currently redirects to Wave-particle duality. &mdash; Cheers, Steelpillow (Talk) 13:16, 13 September 2014 (UTC)
 * I also agree that the name isn't great. The article was previously called de Broglie hypothesis and was changed in January 2009 by User:Chichui, I remember thinking at the time that I wasn't convinced that it is the standard terminology. I don't think there really is a consistent name used for the wave-like nature of matter: "de Broglie hypothesis", de Broglie theory", "de Broglie wave", "particle-wave duality", etc., are all used, and all have their limitations. I wouldn't say that "matter wave" is dumbed down, just a different choice of terminology. But I agree with Steelpillow that "de Broglie wavelength" is only a subpart of what this article is about. Djr32 (talk) 17:21, 14 September 2014 (UTC)

problem in the section headed 'Historical context'
The section headed 'Historical context' contains the following:

"That same year Max Born published his finding that the square of the amplitude of such a quantum wave gives the probability of detecting the particle at any given point in ordinary physical space. He wrote "If one translates this result into terms of particles, only one interpretation is possible. $$\Phi_{n,m}(\alpha,\beta,\gamma)$$ gives the probability [Footnote addition in proof: More careful consideration shows that the probability is proportional to the square of the quantity $$\Phi_{n,m}$$.] for the electron, arriving from the z-direction, to be thrown out into the direction designated by the angles $$\alpha,\,\beta,\,\gamma$$." "

There are problems here.

(1) According to the quote from Born, he is talking about an "interpretation". But the sentence "That same year Max Born published his finding ..." uses the word 'finding', which was deliberately posted to replace the word 'interpretation' by this edit. Likely enough, an ordinary reader will not think that an interpretation is the same thing as a finding. The format of the article seems to agree with such a likely ordinary reader, in so far as it has a separate section headed 'Interpretation', to which material has been moved from the section headed 'Historical context'. It is puzzling as to why the preliminary and less precise article of Born, which speaks of "interpretation", has been restored to the 'Historical context' section, while the more definitive article, which says more or less the same thing, but more precisely, has been moved from the 'Historical context' to the 'Interpretation' section.

It may therefore puzzle the reader as why 'finding' is used in the editorial text but 'interpretation' is used in the immediately adjacent quote from Born.

(2) The editorial sentence "That same year Max Born published his finding that the square of the amplitude of such a quantum wave gives the probability of detecting the particle ..." speaks of "detecting the particle". But the cited articles, by Born, by Heisenberg, and by Bohr, say nothing about detection.

(3) The quote from Born does not support the statement that the probability refers to a "point in ordinary physical space". It would support a statement that the probability refers to configuration space, which is not the same thing as ordinary physical space, as was carefully pointed out, and is still stated in the related quotes in the section headed 'Interpretation', as follows: "In 1955, one of the main contributors to the Copenhagen interpretation, Werner Heisenberg, wrote a considered opinion: "An important step forward was made by the work of Born [Z. Phys., 37: 863, 1926 and 38: 803, 1926] in the summer of 1926. In this work, the wave in configuration space was interpreted as a probability wave, in order to explain collision processes on Schrödinger's theory. This hypothesis contained two important new features in comparison with that of Bohr, Kramers and Slater." Because of this domain of the wave function in configuration space, discussing the meaning of the quantum mechanical formalism, Niels Bohr, the other main contributor to the Copenhagen interpretation, in 1927 wrote "This entails, however, that in the interpretation of observations a fundamental renunciation regarding the space-time description is unavoidable."

The editorial text refers to a "point in ordinary space", while the quote from Born in the section headed 'Historical context' refers to a probability that the electron will be moving in a particular direction, saying nothing about a "point in ordinary space". Motion in a particular direction is however natural in configuration space, which permits changes of dynamical variables, such as changes from one coordinate system to another; here Born uses angular coordinates which do not specify a particular "point in ordinary space".

Therefore, for the ordinary reader, the editorial text contradicts the immediately adjacent quote from Born. This would perhaps puzzle the ordinary reader.

The problems lie in the editorial sentence "That same year Max Born published his finding that the square of the amplitude of such a quantum wave gives the probability of detecting the particle at any given point in ordinary physical space."

(a) It seems hard to see why the word 'finding' has replaced the word 'interpretation' that stood in the past, for example here.

(b) One may question the justification of the mention of detection in the editorial sentence.

(c) It seems hard to see why the editorial sentence explicitly refers to a "point in ordinary physical space", when the wave function has its domain in configuration space.

If the coordinate basis for that space is chosen to be in coordinate space, whether in Cartesian or polar coordinates, then the probability refers to the collected coordinates of all the particles described by the wave function. One might argue, though the present article does not do so, that it is implied or assumed in the editorial sentence that there is a connection between configuration space and ordinary physical space. But if the coordinate basis for that space is chosen to be in momentum space, for example, then the probability refers to momentum space; that is not the same thing as "ordinary physical space", and is the reason why those quoted Copenhagen authors emphasize that the wave function refers to configuration space, not ordinary physical space. The quote from Born in the section headed 'Historical context' is from a preliminary article, in which Born is still groping his way, as indicated by the footnote. The quote from the more definitive article by Born, which has been moved to the 'Interpretation' section, is more precise. It says "...we only have a probability for the choice of a particular path." A path is not a point in ordinary physical space. The particular example of a path given by Born is of motion in a particular direction.

The term "point in ordinary physical space" in the editorial sentence is not supported by the definitive statement by Born; one might even say it is contradicted by it.

In summary then, in general, the wave is in configuration space, not in ordinary physical space. The article should make this clear.

References

Chjoaygame (talk) 02:23, 30 September 2014 (UTC)


 * The editorial sentence could probably be improved, but I am unsure exactly how. First I would make some general points about the encyclopedic context for this information:
 * Many of these issues apply to massless waves such as photons. This article need not itself deal with them rigorously, but it should link to an article which does.
 * A section on "History" is not necessarily expected to be rigorously presented, rather it is an attempt at a narrative. In this respect, some degree of imprecision, oversimplification, etc. is tolerable. We may need to discuss just how much we should tolerate in this particular history section.
 * A quotation such as this one from Born is used to illustrate the historical narrative, it is neither a citation nor an exhibit to be analysed.
 * Turning now to the issues you raise:
 * (1) Born was "interpreting" his wave in a manner which has been experimentally verified, in that he was interpreting his "quantity" as something which can be squared to derive the probability. With respect to the theory, Born's "interpretation" is no longer seen as an interpretation of the theory but has become an integral part of it - we nowadays regard Born's insight as a "finding" rather than an interpretation. The article section on Interpretation is about interpretations of the theory and not interpretations of Born's "quantity". This kind of natural ambiguity and imprecision in language is extremely common and most readers will unconsciously understand and tolerate it, but if we agree that this example is unusually serious then we can address it.
 * (2) On detection; a quotation does not need to support every statement made in the editorial commentary, it is merely illustrative of the historical context being described by that narrative. As such, the absence of the word "detection" from the quotation is not significant. By contrast, if the editorial omits the word, there is a risk of assuming that "the particle" is "there" even when not being measured - an assumption which is denied by the Copenhagen interpretation and which therefore must be treated in itself as an interpretation. So I do think that the presence of the word "detection" in the narrative is significant.
 * (3) Turning now to the "point in ordinary physical space." I agree that this is not very useful and should be improved. As you say, we are often dealing with some other condition than an identifiable point. However, while the wave propagates in configuration space, experimental measurements take place in ordinary space. I am not aware that the relationship between these two kinds of space has ever been satisfactorily resolved. I would not be able to source a mainstream discussion on this point and on that basis all that I can suggest in the present article is to gloss over it in much the same way that the mainstream sources I have seen appear to. If you know different, that would be good. Otherwise, perhaps we could change the editorial text to something along the lines of, "...the probability of detecting the particle under any given condition."?
 * Does any of that make sense? &mdash; Cheers, Steelpillow (Talk) 11:43, 30 September 2014 (UTC)


 * Thank you for this response. Chjoaygame, about 20:05, 30 September 2014.

Wikipedia should be neutral
There are defects in the new edit. It is not Wikipedia neutral.

It is theft of ideas to attribute the idea of matter waves to quantum mechanics, as does the new first sentence. They were invented by de Broglie before quantum mechanics.

Moreover, the idea of matter waves is interpretational not directly factual, as shown by the disagreement between Bohr and Heisenberg about this. And indeed between them and Schrödinger. It is bad to say that quantum mechanics "has shown" something that was an assumed ingredient or postulate or intended interpretation. The new first sentence of the lead is more triumphalist propaganda than neutral Wikipedia reporting of reliable sources.

A Wikipedia neutral way to go would be to demote the quantum mechanics to a later place, following the info about de Broglie, and to use, instead of the very dubious and tendentious "shows", words such as 'recognizes' or 'expresses the idea'.

Matter waves are more interpretational than factual. De Broglie thinks of them differently from how quantum mechanics does. The article should make this difference clear, not obscure it as it does at present.

The new edit claims that " the de Broglie hypothesis is a central part of the theory of quantum mechanics, and is crucial to the modern theory of atomic structure and particle physics". This is interpretational and not factual. Moreover, it is not essential to this article. It is a claim primarily about quantum mechanics and the modern theory, only derivatively about matter waves. It is not detailed in the body of the article, and is unsourced; for such a claim, very good reliable sourcing would be needed. It hardly has a place in a neutral lead for this article.Chjoaygame (talk) 22:22, 16 November 2014 (UTC)
 * I agree that the lead should not begin with the words "quantum mechanics" but my reasons differ. Most fundamental ideas in quantum mechanics were formulated before quantum mechanics was. Quantum mechanics arose as the framework that stitched them all together into a coherent whole. To claim that it "stole" a preceding theory is ridiculous, like claiming that Newton "stole" Kepler's discovery that planets orbit in ellipses. The issue as to whether the term "matter wave" denotes the theoretical formulation, the observed behaviour, or some underlying reality, is also invidious. It refers to whichever of these is currently under discussion, often tacitly to all three. That is the way language works. All three are relevant to this article and all three deserve equal, if appropriately delineated, emphasis. Nor do I think that an emotive word like "triumphalism" can do anything more than cloud any valid point surrounding it. No, my only quibble is that we should mention the title topic before we discuss its applicability.
 * I would prefer the lead to begin along the lines of, "Matter waves, often called de Broglie waves, are an aspect of wave-particle duality. In quantum mechanics, every particle may behave as a wave and vice versa. The wave behaviour of massive particles was first predicted by Louis de Broglie and provided one of the foundations on which quantum mechanics was built." In practice, how acceptable is that? &mdash; Cheers, Steelpillow (Talk) 23:01, 16 November 2014 (UTC)


 * It isn't quantum mechanics. It is the Wikipedia editor that is the thief. The word triumphalism is from the reliable literature, complaining about emotionalism such as is perpetrated by the edit.Chjoaygame (talk) 00:48, 17 November 2014 (UTC)


 * I was struggling with how to get the title into the first sentence, but in the end I decided it was better instead to start with the key point that "all matter has wave-like properties". To me, "an aspect of wave-particle duality" should come later - any reader who doesn't know that matter behaves like waves won't be left any the wiser by reading this - and I couldn't think of a comprehensible sentence which achieved both things. I think this is related to the issue we discussed in September that there isn't really a clear title for this concept, and so we have ended up with 4 different possible titles in bold! Djr32 (talk) 23:36, 16 November 2014 (UTC)


 * Electrons, atoms, molecules are definitely matter, and definitely diffract. It is nonsense to suggest that the wave-like behaviour of matter is "interpretational and not factual". The major steps in the development of QM were Planck (1900), Einstein (1905), Bohr (1913), de Broglie (1924), Schrodinger/Heisenberg (1926). De Broglie is a central part of this story, a key step from the old quantum theory to the new, not a separate story whose ideas are being plagiarised. Djr32 (talk) 23:17, 16 November 2014 (UTC)


 * Dear Djr32, you think Heisenberg was talking nonsense when he accepted the Duane concept. Silly old Heisenberg, he needs to read Wikipedia to get the right story. My concern is not alleged plagiarism by de Broglie; it is muddle in Wikipedia.Chjoaygame (talk) 00:48, 17 November 2014 (UTC)
 * How about, "That matter has wave-like properties is an underlying principle of quantum mechanics."? This catches the visitor's midset directly and leads the reader into the context, rather than dumping them in it and then throwing in the relevance.
 * FYI it is apparently possible to interpret diffraction in terms of particles and momentum transfer. The wavelike behaviour is then seen as an emergent property of the particle system. I have seen highly respected physicists scorn such primitive intuition, while OTOH somebody at the WikiProject Physics talk page ranted at me how this was standard in the text books. Not having a good selection of textbooks, I cannot judge the truth of that, but certainly the controversy rages as fiercely in some quarters as it did eighty years ago. As ever, fanatical belief and polemic get muddled with objective fact in the protagonists' minds. They see it as essential to sneak their "wholly rational" metaphysical interpretation into the mix, and a genuinely objective form of words is seen by them as a sell-out to the other camp.
 * I have seen critiques of Hesisenberg, again by highly respected physicists, which described how he struggled with the interpretation of his uncertainty principle all his life, long clinging to the idea that it was merely a limit to measurement of the underlying "common-sense" reality. Only late in life, if at all, did he come to accept that it was a fundamental characterstic of some bafflingly counter-intuitive reality. It seems from remarks made above that this affected his thinking on wave-praticle duality too.
 * Objectively, the wave-like behaviour is undeniably wave-like. And it is undeniably of note primarily for its place as a foundational aspect of quantum mechanics. To treat it in any other context is absurd. Whether we have massive particles and some hand-waving mysticism about quantal momentum transfer, or whether we have hand-waving mysticism about something else, or whether we follow the Copenhagen advice and keep our hands in our pockets, should be banished to the section on "Interpretations" and not snuck into the lead. IMHO every physics student should be required to read WP:LEGS at the start and end of every semester.
 * &mdash; Cheers, Steelpillow (Talk) 09:05, 17 November 2014 (UTC)


 * I tried reorganising it a bit. "That matter has wave-like properties..." feels a bit awkward and still doesn't include "matter wave", but I don't particularly like my version either so feel free to change it if you like.
 * I have tried to work out what your comment means, but I'm none the wiser. Perhaps you could suggest a specific change, and we can discuss whether it's an improvement or not? Or explain what you think is wrong with a particular sentence? Djr32 (talk) 21:29, 17 November 2014 (UTC)

problems with recent edit
I think there are a number of significant problems with Chjoaygame's recent edit to the lead. To list the most significant:
 * The first sentence is "The concept of the matter wave was invented in 1923 by Louis de Broglie." I think this is a bad way to start: we should start by saying what a matter wave is, not with the history of the concept.
 * It continues "He proposed that particles of matter have intrinsic internal periodicity in their own rest frames. To observers, seeing them move past, they would therefore exhibit wave-like phenomena." This is nonsense. (Simple proof: if the frequency was intrinsic to the particle, the wavelength would be the distance that the particle travels in one period, i.e. the wavelength would be proportional to momentum. De Broglie, of course, proposed that the wavelength is inversely proportional to momentum.)

Therefore I have reverted the change. Djr32 (talk) 23:58, 18 November 2014 (UTC)


 * To find out what de Broglie proposed, one way is to read scholarly work about it and check that against de Broglie's actual publications.Chjoaygame (talk) 00:48, 19 November 2014 (UTC)
 * But one cannot cherry-pick scholarly works in order to make a point. On Wikipedia, secondary and tertiary works are preferred to primary research. Like it or not, a populist but well-researched work like How the Hippies Saved Physics carries more editorial weight than an original paper. If you must resort to original papers to construct a long and wordy argument, you are surely moving away from the mainstream and falling into the logical agonies so graphically explained at WP:LEGS. Note to self: try and find time to raid my book shelf. &mdash; Cheers, Steelpillow (Talk) 04:23, 19 November 2014 (UTC)
 * @Djr32. Yes, that kind of word tangle is not appropriate to an article lead. I would add that "invented" is also the kind of subtle perjorative that we need to guard against. Theoretical physicists do not "invent" theories, they may develop or propose them or, ultimately, discover a law of nature. We also need a more suitable reference than de Broglie's own work, i.e. one which discusses de Broglie's contribution in context. &mdash; Cheers, Steelpillow (Talk) 04:23, 19 November 2014 (UTC)


 * Pejorative?
 * De Broglie on page 110 of Schilpp 1949: "It is not to the discredit of great inventors to say that a discovery always comes "in the fulness of time" ..."
 * Einstein in his Herbert Spencer Lecture 1933: "Apart from that, these latter are free inventions of the human intellect ..."
 * As for a suitable reference, more or less popular and well researched, what about the one from Physics Today that our friend deleted without reading it?Chjoaygame (talk) 09:30, 19 November 2014 (UTC)


 * The only reference that was added was in support of the paragraph which stated "Since then, matter waves, also called de Broglie waves, have been observed for many kinds of particle, sub-atomic, atomic, and molecular." This sentence isn't in question, the other version said the same thing in different words: "it has also been confirmed for other elementary particles, neutral atoms and even molecules." There are already 10 references in the Experimental confirmation section to cover this, but I certainly have no objection to one being added to the lead. However, this is a minor detail, the main issue is that what you wrote in the first paragraph is nonsense. Perhaps you could address this? Djr32 (talk) 12:23, 19 November 2014 (UTC)


 * The reference covers and is the source of all that precedes it, as you would have found by reading it. The "nonsense" of which you complain is what the reference says de Broglie proposed, and can be checked in his publication, if you had read them. It is not customary to heavily pepper the lead with repeated references.Chjoaygame (talk) 13:15, 19 November 2014 (UTC)


 * If you claim something in the first paragraph which disagrees with pretty well physics textbook I have ever seen and isn't supported by anything written in the rest of the article then, yes, you do need to provide a reference for that specific fact. Adding a reference several paragraphs away to a 40 year old review paper is not an alternative. Djr32 (talk) 18:32, 19 November 2014 (UTC)

de Broglie referred to the wave as "fictitious"
In his first 1923 paper De Broglie referred to the phase waves as "fictitious". In his next paper he referred to them as "non-material". They are faster than light. In his 1960 book, de Broglie wrote "... the wave did not actually describe reality". Real physical oscillatory waves are manifest in 'displacement' of some actual physical quantity, for example electric field intensity, or gas pressure. De Broglie does not offer an actual physical displaced quantity, beyond writing of "phase waves". That makes his waves apparent and virtual, as he says "non-material", and unable to carry energy, though perhaps not "fictitious". Since the phase wave cannot carry energy, it is remarkable that the group wave can do so.Chjoaygame (talk) 15:02, 29 November 2014 (UTC)


 * I reverted your edit not least because you mixed up several things:
 * The term "phase wave" is not usual in wave theory. de Broglie introduced it with a specific meaning that needs explaining here. See for example http://www.ontostat.com/anglais/phase%20wave%20gb.htm
 * Whether or not the main matter wave is real or virtual is a matter of interpretation. There is a separate section for that.
 * De Broglie's own beliefs as to the correct interpretation are not relevant to modern treatment - they need to be presented either in the section on Interpretation or in the History section.
 * The mix-up continues in your comment above, especially as to whether you are discussing the as-yet unexplained "phase wave" or the usual mass-carrying wave at each mention. &mdash; Cheers, Steelpillow (Talk) 16:24, 29 November 2014 (UTC)

De Broglie's initial steps
Thanks for the references to de Broglie's thesis and assessments of it, User:Chjoaygame. I had a lot of projects at work with deadlines just before Christmas, but I've finally had time to follow up on them over the break! It's interesting to read about how de Broglie struggled with producing a coherent theory, and changed his fundamental hypotheses as he tried out different ideas, which is something I had never been aware of before. I think they do demonstrate why it's better to work from modern secondary sources rather than relying on interpreting quotes from de Broglie: as MacKinnon says, the "formula proved successful, though the theory supporting it rested on a conceptual confusion", so I don't think we want to spread conceptual confusion to our readers. Anyway, a belated thanks for some interesting reading and discussion over 2014, and a happy new year to you! Djr32 (talk) 00:21, 4 January 2015 (UTC)

MATTER WAVE CAN BE SHOWN TO HAVE SIMILAR FORMATION TO THE ELECTROMAGNETIC WAVE
By applying Dirac equation it can be shown that matter wave has a similar mathematical formation to Maxwell field equations, both systems of field equations in turns can be derived from a general system of linear first order partial differential equations. In particular, like Maxwell field equations, Dirac field can also be formulated as a system of real equations and quantum particles can be shown to manifest as string-like objects whose cross-section vibrates as a membrane. Please refer to an article entitled ON THE NATURE OF MATTER WAVE posted on ResearchGate by Vu B Ho for more details.101.189.23.61 (talk) 05:15, 22 February 2018 (UTC)

Gouanère et al. 2008 confirmation of ~10^21 Hz electron's clock?
The best confirmation of electron's ~10^21 Hz de Broglie clock I have heard of (from Hestenes https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.169.7383&rep=rep1&type=pdf ) is the 2008 "A Search for the de Broglie Particle Internal Clock by Means of Electron Channeling" Gouanère et al. paper ( https://link.springer.com/article/10.1007/s10701-008-9225-1 ): for high energy ~81MeV electrons, due to time dilation the distance between "ticks" of such clock agrees with ~0.4 nm lattice constant of silcon crystal - they observe increased absorption.

I don't see it in this Wikipedia article - should it be added? --Jarek Duda (talk) 14:38, 21 March 2021 (UTC)

A more general issue with the historical context section
A more general issue with the historical context section is that all of the content that you are discussing isn't historical context.

In some senses, matter waves don't have a historical context, any more than the circulatory system has a historical context: it's a property of nature which exists independently of de Broglie, Schrödinger and Born. On the other hand, it does make sense to cover the historical context of de Broglie's hypothesis: what question was de Broglie attempting to answer, what was the state of science beforehand, etc. However, historical context is the background to the thing, not the thing itself: everything beyond "light has both wave-like and particle-like properties" doesn't belong here.

There is, of course, an argument for discussing matter waves through the history of the discovery, and the de Broglie quote could fit in there. But after that, the section leaps straight into a very abtruse discussion of the interpretation of wave functions (i.e. not exactly the same thing) which is already covered in the wave function article. Having this here without covering the necessary background makes the article worse rather than better, so I propose deleting it. Djr32 (talk) 20:35, 30 September 2014 (UTC)


 * I am sympathetic to the idea of deletions here. Recently I made one with the usual polite edit summary wording of this article "Remove hopeless technobabble" but my deletion was immediately undone.


 * It is not clear exactly what you propose to delete. Perhaps you will clarify, or just do it?Chjoaygame (talk) 03:40, 2 October 2014 (UTC)


 * I had in mind doing pretty well what you did above. I'll do it later on, maybe with a more detailed edit summary to see if it convinces people. Djr32 (talk) 16:54, 2 October 2014 (UTC)
 * With the advantage of some 8 years delay I have "solved" the history issue here. I removed the redirect from De Broglie hypothesis and moved all of the de Broglie focused history to that new page. Which is also almost all of the History of Matter Wave.
 * This gives us space to have the History on Matter wave devoted to the subject rather than to de Broglie.
 * Johnjbarton (talk) 01:49, 10 May 2023 (UTC)

Example Matter Waves seen experimentally
I generated a table with Jupyter using my personally created MatterWave.ipynb.

I placed the table directly after the introduction of wavelength, to give the reader an overview of the content which follows as well as an overview of the typical wavelengths used in experimental confirmations.

Johnjbarton (talk) 18:47, 9 May 2023 (UTC)


 * @Johnjbarton, I am reverting the article back to the state it was in on March 23. You are an inexperience editor and need to be more familiar with Wikipedia's encyclopedic style before making such sweeping changes.
 * Wikipedia articles have a structure. The lead summarizes the rest of the article and does not contain tables. Details belong in the sections below. Examples belong at the end if at all. The reasons behind the development need to be included at the beginning. The "Scope of Matter Wave Behavior" is written in an essay-like manner and as written seems to have little relation to the sources used.
 * , this has removed your additions. I will try to put them back at the appropriate places. StarryGrandma (talk) 05:30, 14 May 2023 (UTC)

Needs citations, and there is some duplication
Some issues:
 * A lot of material is introduced without sourcing. I have added some for the electron diffraction part, including correcting some
 * I think there is duplication in several places.
 * The first image worries me. I have corrected the description, but that is not enough. Almost certainly it should be contrast reversed, and referenced to the work of Tonamura or others. I believe it is numerical, but tracking to its source does not say.
 * I do not think the flow is good, and the grammar needs a little cleaning.
 * Some use of words such as "we" or "one", which it is better to avoid. Also the relevance is not just to Physics.￼
 * I think partial coherence & group velocity need to be included. Incoherence as a standard transition to classical.

Ldm1954 (talk) 22:23, 13 May 2023 (UTC)


 * As an addendum (kept separate for simplicity), in at least the "Neutral atoms" section some of the references are not quite right. For instance, Fresnel diffraction is referenced with a paper where zone plates are used to focus atomic beams. These need repair, including reading all the relevant refs. Ldm1954 (talk) 17:47, 15 May 2023 (UTC)

Reverting to the March 23, 2023 version
@Johnjbarton, I am reverting the article back to the state it was in on March 23. You are an inexperience editor and need to be more familiar with Wikipedia's encyclopedic style before making such sweeping changes.

Wikipedia articles have a structure. The lead summarizes the rest of the article and does not contain tables. Details belong in the sections below. Order of the sections and development of the material matters. Readers need to be able to follow the topic. Examples belong at the end if at all. Historical reasons forthe development need to be included at the beginning. The "Scope of Matter Wave Behavior" is written in an essay-like manner and as written seems to have little relation to the sources used.

, this has removed your additions. I will try to put them back at the appropriate places. StarryGrandma (talk) 05:34, 14 May 2023 (UTC)


 * , you are correct that the article needs a lot of work and material needs to be removed. But as you make changes it still needs to be a comprehensible and well-organized article at each step. Please read Summary style which says Sections of long articles should be spun off into their own articles, leaving summaries in their place. and explains how to do this. Always put a summary in place as you remove material to another article, and include a link to the other article at the top of the summary. StarryGrandma (talk) 17:32, 14 May 2023 (UTC)
 * @StarryGrandma, the state you have left the article includes long historical sections at the end, against your guidelines. "Interpretations" is mislabeled: it is mostly historical material related to de Broglie; just read the first sentence. Similarly the section "De Broglie's phase wave and periodic phenomenon" discusses issues in de Broglie's 1924 thesis.
 * More important, these large sections detract from the focus on Matter waves. They make the subject appear to be of controversial and historical interest. That is why I decided to spin it off.
 * I did indeed spin off the removed material into the page De Broglie hypothesis. I did indeed leave a summary in place and I linked the new page from my summary. As far as I can tell, I did exactly as you Summary style suggests.
 * I do not agree that you have left a comprehensible and well-organized article after your step. As you said yourself the article needs a lot of work, which I contributed and you removed.
 * It seems to me that two simple changes would have corrected the majority of your concerns:
 * 1) moving the History section up,
 * 2) move the example table down in to the subsection.
 * To be honest you actions are very discouraging. I came here hoping to make the world just a tiny bit nicer. I posted small changes and requests for feedback but heard nothing. Then all of my work was reverted.
 * In my opinion some small, important edits on your part with some encouraging pointers in the right direction would be much much more appropriate. Johnjbarton (talk) 17:15, 16 May 2023 (UTC)
 * @Johnjbarton, almost no one who starts editing here has ever written for an enclopedia before, and there is a learning curve. Writing for Wikipedia is quite different from writing journal articles or textbooks. Editors don't talk directly to readers as in texts. Editors don't analyze material and draw conclusions as in school papers or journal articles. Articles are written in a collaborative atmosphere, with many editors contributing content and continuing to watch changes to articles. New material is frequently questioned, altered, or removed, particularly because it takes new editors time to become familiar with editing here. Discussion then moves to the talk page of the article. Don't be discouraged; this is just how editing here works. How else would anyone learn how to edit here except by jumping in and making changes and seeing what happens? We are in need of editors who understand technical material and I hope you keep going with this.
 * The two issues that you mention, the table in the lead and putting all the history at the end are just problems with position. Lets talk about the major issues.
 * A topic like this that is important in the history of quantum mechanics is not just about the current state of the field. It needs to provide the rational for the concept as well as its developement over time and experimental confirmation. Where the idea comes from needs to be up front, as it is with the section "Historical context". Information about the De Broglie hypothsis comes next, because it came next. The equations need to be explained in this section. The lead paragraphs just summarize the article content, so having the equations in the lead isn't enough. They also need to be explained at the beginning of the article. This is where the summary of De Broglie hypothesis should be. Summary style means having a section devoted to the summary with a link at the top of the section to a main article using Template:Main. It will look like this:
 * The "Experimental confirmation section" should not be called an example section - they are developments in the history of the concept. The "Neutral atom" section should also show the chronological development. Instead you changed it from prose to a bulleted list in alphabetical order. As Manual of Style says Do not use lists if a passage is read easily as plain paragraphs. It needs summary text with discussion of early experiments, etc. You can expand Atom optics with prose descriptions of the material in the list you provided. In this case, since this article is just about matter waves, and not all those other topics, the link at the top of the section uses  since there should be further reading about those topics there.
 * In "Scope of Matter Wave Behavior" the sources do not match the statements. You may have been drawing your own conclusions here. The article hasn't talked about matter wave interferometry up to this point, and the whole area is complex enough to be left to another article and only mentioned in this one. We write as much as possible for the general reader, and you have jumped deep by introducing quantum decoherence here. It should be left to the interferometry articles.
 * You are right that the article is not in great shape and needs a lot of reworking. Throw out the "Interpretations" section again. Articles in this area of quantum mechanics have just been added to and created by various editors at various times. You may have to figure out how articles like Wave particle duality and Electron interferometer fit in. The current term for Atom interferometer seems to be matter wave interferometry, not limited to atoms or electrons. StarryGrandma (talk) 23:06, 16 May 2023 (UTC)
 * @StarryGrandma Thank you for the information about the structural requirements for Wikipedia pages.
 * "Don't be discouraged; this is just how editing here works."
 * I don't have any problem with collaboration, discussion, or review. But I also don't plan to spend hours for zero results.
 * Based on Be_bold it seemed to me that issues with my edits would be followed with improvements or Talk Topics. I noticed that you did not revert based on particular edits but rather exactly all of my edits on the page. My takeaway is "get lost" not "this could be better if you..."
 * "A topic like this that is important in the history of quantum mechanics is not just about the current state of the field."
 * I do agree that an comprehensive historical outline with experimental examples would truly be wonderful. However Top-importance physics article should reflect the state of physics today as much as reviewing historical path behind. Today's page only accidently mentions recent work.
 * "The "Experimental confirmation section" should not be called an example section - they are developments in the history of the concept."
 * In my opinion developments in the history of the concept of matter waves should be organized chronologically, not by a particle type. Given the current outline I tried expand on the particle type theme as that allowed many new links and references to fit in naturally.
 * "In "Scope of Matter Wave Behavior" the sources do not match the statements."
 * I agree that this effort was premature.
 * "You are right that the article is not in great shape and needs a lot of reworking."
 * We are approaching the 100th anniversary of the de Broglie hypothesis. So much has happened in physics over those 100 years! Wikipedia deserves better than a "C-Class physics articles of Top-importance" for Matter wave. Johnjbarton (talk) 00:34, 17 May 2023 (UTC)
 * @Johnjbarton, it would be lovely to have this evolve into a much better article. But you changed the focus of the article from one that started with the historical development that shows why we accept matter waves to one beginning instead to focus on the current state of the subject. That is quite a change, and why I didn't see any way to just make some changes to what you had done. There is almost nothing in the current article about current research in matter waves. What you apparently want to do is replace the content of this article almost entirely which is concerning. Compare Introduction to quantum mechanics with Quantum mechanics. That is a big enough topic that it is spread over two articles, the second being fairly impenetrable to non-scientists. In this article we need to do both, provide the material that explains how the subject came to be and what it is to general readers as well as provide more technical detail. The current article starts out with the historical background, and I am objecting to the change in approach. StarryGrandma (talk) 01:48, 17 May 2023 (UTC)
 * Starting with historical background -- being background -- would not be my preference. However, you say that's the style, so now I know.
 * I do not think the History section should scattered over misnamed top level sections "Experimental Confirmation" "De Broglie Hypothesis" or "Interpretation" and "De Broglie's phase wave and periodic phenomenon" as current. Combining the content under "History" would be an improvement. Then at least the Confirmation section would not seem to be about the topic and the odd bits at the end would maybe make sense, IDK. Johnjbarton (talk) 02:23, 17 May 2023 (UTC)
 * I agree that the first few sections work better as subsections of "History". I am not sure what the point of the "De Broglie's phase wave and periodic phenomenon" is. I suppose there is value in explaining de Broglie's original argument (which uses special relativity in a way that most modern introductory courses in quantum mechanics tend to avoid), and I can see the merit in keeping the details out of the mainline of the historical treatment (they're not needed for a synopsis). But it's not clearly written at all. XOR&#39;easter (talk) 15:21, 17 May 2023 (UTC)
 * Of course I agree. The only critical bit of that section, the application of special relativity to frequency, is already covered in the "Group velocity" subsection, albeit unreferenced. Similarly the "de Broglie hypothesis" subsection includes this cryptic sentence: "He also referred to Einstein’s famous relativity equation."  (This reader thinks: which famous equation? referred? used? how? to what purpose?) Johnjbarton (talk) 17:20, 17 May 2023 (UTC)
 * Yes, I noticed that and have now taken a crack at revising it (further improvements are doubtless possible). XOR&#39;easter (talk) 18:14, 17 May 2023 (UTC)
 * I think your copying from the Schroedinger equation section has introduced an error. There is the time-independent form, and here the modulus squared of the wavefunction times electron charge is the time-averaged charge density, e,g. what is measured in XRD. I think you overstate, or those sources do.
 * Just a minor comment, I realise that this is a work in progress. Ldm1954 (talk) 12:44, 18 May 2023 (UTC)
 * Also...I see that other parts have been copied from elsewhere, so probably have errors. For instance in many articles (and previously here) Alexander Reid was not mentioned in the Aberdeen transmission electron diffraction experiments, and the sample was stated to be a metal film (it was celluloid, a plastic). Ldm1954 (talk) 20:25, 18 May 2023 (UTC)
 * The "Interpretations" section was a trainwreck: unclear, meandering, superfluous, and historically inaccurate. I mean, it starts a paragraph by saying These ideas may be expressed in ordinary language as follows and then follows that with explicitly express the Aristotelian idea, referred to by Newton, Green's functions, and observed quantal phenomena. XOR&#39;easter (talk) 15:06, 17 May 2023 (UTC)
 * Yes, I noticed that and have now taken a crack at revising it (further improvements are doubtless possible). XOR&#39;easter (talk) 18:14, 17 May 2023 (UTC)
 * I think your copying from the Schroedinger equation section has introduced an error. There is the time-independent form, and here the modulus squared of the wavefunction times electron charge is the time-averaged charge density, e,g. what is measured in XRD. I think you overstate, or those sources do.
 * Just a minor comment, I realise that this is a work in progress. Ldm1954 (talk) 12:44, 18 May 2023 (UTC)
 * Also...I see that other parts have been copied from elsewhere, so probably have errors. For instance in many articles (and previously here) Alexander Reid was not mentioned in the Aberdeen transmission electron diffraction experiments, and the sample was stated to be a metal film (it was celluloid, a plastic). Ldm1954 (talk) 20:25, 18 May 2023 (UTC)
 * The "Interpretations" section was a trainwreck: unclear, meandering, superfluous, and historically inaccurate. I mean, it starts a paragraph by saying These ideas may be expressed in ordinary language as follows and then follows that with explicitly express the Aristotelian idea, referred to by Newton, Green's functions, and observed quantal phenomena. XOR&#39;easter (talk) 15:06, 17 May 2023 (UTC)

Unreferenced, dubious claim in introduction concerning wavelength
The current introduction says:

"In most cases, however, the wavelength is too small to have a practical impact on day-to-day activities."

I believe this sentence is an attempt to answer a very important question readers will have about matter waves: "Why don't I see these things??".

However the "wavelength is too small" explanation does not match any experimental or theoretical result that I am aware of.

I previously replaced this sentence with one which derives from experimental evidence (see Quantum_decoherence):

"The vast number of interactions in the solids, liquids, and gases we interact with daily suppress this quantum wave behavior."

However @StarryGrandma objected when I used a decoherence link in a reverted edit: "We write as much as possible for the general reader, and you have jumped deep by introducing quantum decoherence here. It should be left to the interferometry articles."

IMO simply replacing the dubious sentence with my proposed edit improves the content. I would leave it unreferenced to avoid jumping deep.

Suggestions? Johnjbarton (talk) 23:58, 17 May 2023 (UTC)


 * Some version of "the wavelength is too small" is all over introductory texts. See, e.g., chapter 1 of Griffiths or McQuarrie (calculating the de Broglie wavelength of a baseball seems to be a favorite example, for some reason). Even if it's only a heuristic for why these phenomena are far removed from daily experience, it's a heuristic that every student is exposed to, and we can't really junk it. We could say more in addition to it, but leaving it out would skew our portrayal of the literature we're supposed to be summarizing. Whatever we say has to be referenced in some manner so that the reader can check up on it. This doesn't necessarily mean a footnote after every sentence, of course, though one per paragraph is often a good rule of thumb, since a paragraph is supposed to be a set of sentences working together to express an idea. Statements in the intro of an article often go without footnotes if they are explained at greater length in the main text below. That would be the route to go here, I think. XOR&#39;easter (talk) 01:43, 18 May 2023 (UTC)
 * I personally have issues with the "Quantum decoherence" concept, as would anyone with a strong optics background. Coherent (laser) and incoherent (light bulb) illumination are standard. Coherency can be improved with small apertures (for instance, as we did in high school), destroyed by inelastic scattering. A good text on this is Born & Wolf where partial coherency is introduced, and there is a stub coherence theory. In QM this gets into density matrices, and perhaps second quantization. In electron optics the concept of a "transverse coherence length" is standard -- beyond this two points weakly interfere. This is a measure of the size of the electrons.
 * The standard way (in EM) to teach the transition from quantum to classical is as the limit where the coherence lengths tend to zero. A coherent baseball would diffract!
 * I think a section similar to this is needed to avoid confusion about QM versus classical. Ldm1954 (talk) 13:05, 18 May 2023 (UTC)
 * Yes, "decoherence" was co-opted by Zeh and others on the theory side to mean environmental entanglement. Nevertheless the experimental work on environmental degradation of interference gets labeled as "quantum decoherence" even though no evidence supports the connection. (And to be sure the QM to classical transition may not be all about coherence).
 * But maybe this suggests a path for Matter Wave: discuss degradation of interference experiments directly and link to "quantum decoherence" as one theory.
 * I feel like untangling the many interesting but sometimes conflicting meanings of "coherence" should be else where. Johnjbarton (talk) 15:19, 18 May 2023 (UTC)
 * Ok thanks. I guess textbooks don't have to cite their sources or go through peer review. They often have a strong point of view.
 * I do like the baseball idea though: concrete examples of de Broglie wavelengths to drive home the difference in scale. Johnjbarton (talk) 15:04, 18 May 2023 (UTC)
 * I suggest to Johnjbarton, XOR&#39;easter and doing some basic repairs first. For instance, the section has zero citations. While we all know roughly what they should be, they are needed for readers who do not. While adding the relevant citations my experience is that one thinks "Oh, that needs to be added to explain". Then the section builds to something coherent (not a pun) and stand alone. For instance, is that section the right place to mention the use of $$f$$ for frequency? Indeed, why not just use $$f$$ everywhere. With a complicated article such as this I would repair it section by section first. Later you may even want to come back and amend some of these, both from more thinking and feedback from others.
 * N.B., I agree about "decoherence". For later. Ldm1954 (talk) 15:24, 18 May 2023 (UTC)

"Controlled double-slit electron diffraction" for images, video.
| Controlled double-slit electron diffraction is a short readable article on the 'iconic' double slit experiment for electrons. Even discusses Feynman ;-)

Images are Creative Commons 3.0.

The supplementary data includes a .MOV showing build up of the diffraction pattern from individual events.

To use the content it needs to be Converted However, evidently one must be a committed user of wikimedia (30 edits?) to use the converter.

@Mike_Peel do you have any suggestions. Johnjbarton (talk) 16:28, 18 May 2023 (UTC)


 * Nevermind! I found a way: ffmpeg on a PC and upload to Wikimedia.
 * [[File:Electron_buildup_movie_from_"Controlled_double-slit_electron_diffraction"_Roger_Bach_et_al_2013_New_J._Phys._15_033018.webm|thumb|Double slit electron diffraction pattern building up electron by electron.]]
 * Johnjbarton (talk) 00:53, 19 May 2023 (UTC)
 * Used
 * to create a looping gif instead:
 * [[File:Electron_buildup_movie_from_"Controlled_double-slit_electron_diffraction"_Roger_Bach_et_al_2013_New_J._Phys._15_033018.gif|right|thumb|200x200px|Matter wave [[double slit diffraction]] pattern building up electron by electron. Each black dot represents a single electron hitting a detector; with a statistically large number of electrons interference fringes occur. ]] Johnjbarton (talk) 00:34, 20 May 2023 (UTC)
 * Installed the GIF into Matter_wave
 * @Ldm1954 please check Johnjbarton (talk) 00:49, 20 May 2023 (UTC)
 * The image looks good. Just be aware that this was done earlier by Tonamura in Japan & even earlier in Italy by Pozzi in 1973 -- see the double slit page. I suggest slight wordsmithing. In fact the work by Mollenstat is earlier, around 1955, not quite a double slit but similar -- interference from a wire as an attractor. Ldm1954 (talk) 02:01, 20 May 2023 (UTC)
 * Ok I think I improved the paragraph, adding both refs. I am satisfied with this section for now. Johnjbarton (talk) 16:30, 21 May 2023 (UTC)
 * I corrected the "black" to "white", it is fine otherwise. Ldm1954 (talk) 16:33, 21 May 2023 (UTC)
 * I corrected the "black" to "white", it is fine otherwise. Ldm1954 (talk) 16:33, 21 May 2023 (UTC)


 * References

Angular units confusion
There is a pervasive abuse/confusion of terminology around angular quantities in textbooks and engineering texts. As I understand it, WP (being a encyclopaedia) is build around topics, not words (as would be the case for a dictionary), as per . An example of a transgression might be the "popular" use of frequency to denote angular frequency, and using this to argue that since the name "frequency" is used in this way in sources (including defining the symbol f = &omega;, and 1 Hz = 2&pi; rad/s), a discussion of angular frequency as used in these sources therefore belongs in the the article Frequency. The article Wave vector (older version linked) is an example of such a conflation of two related but distinct concepts into one article (they could be, but they should be separated terminologically within the article). I have made the change wave vector &rightarrow; angular wave vector here because one does want to know which applies.This is more a rant than anything else, but I would appreciate any feedback from real physicists on the handling of this matter: if I am being silly in your opinion, I will retire from such clarifications altogether; I have recently totally withdrawn from dealing with this in the actual articles dealing with these quantities due to pushback from a few otherwise unopposed vocal editors (too much pushback from the popular-use proponents, and minimal support for (or maybe understanding of) my perspective about separation of concepts at WT:PHYS). —Quondum 12:54, 19 May 2023 (UTC)


 * IMO there are two issues here.
 * One is using abbreviations that using "frequency" as an abbreviation for "angular frequency". Here I think MOS:ACRO1STUSE would apply.
 * The second, and tougher, issue is contextual ambiguity. So experts in two fields will use "frequency" and assume that this is known to all interested readers. Of course that is not the case and you efforts can help.
 * In your particular example, it took me several minutes of study to figure out what "angular wavevector" could possibly mean. I've simply never heard that combination and did not consider "wavevector" to be an abbreviation for any thing.
 * Now I realize that combination "angular wavevector" is an awkward abbreviation for "angular-wavenumber vector". It's confusing to combine two unrelated directional concepts "angular" and "vector" in one word. For this reason I'm not a fan of wave vector → angular wave vector. Based only on my own personal experience (and perhaps the experience of the previous editors of the wavevector page), the primary concept is "wavevector" and the rare exceptional case is "angular-wavenumber vector", which is anyway just a change of units.
 * HTH Johnjbarton (talk) 01:54, 20 May 2023 (UTC)
 * I'm evidently not explaining this too well. I have no issue with different disciplines shortening phrases where this does not create within the context, or repurposing names (unfortunate as it is, it is unavoidable).  Wikipedia is naturally a very broad context, and so care is needed.  For example, even though an article falls within a discipline where angular frequency is routinely called frequency, if this is done in an article, this abbreviation must be defined within the article, and when linking, one would need to link as frequency.  In this context (i.e., WP), it is often simpler and clearer just to preferentially expand the abbreviated form, though.
 * What I do have an issue with is when homonyms get conflated as concepts on WP (your second issue), and it seems clear to me that WP editors are confused about this. Your statement "... which is anyway just a change of units" needs to be rethought: that is akin to saying that the circumference is just a change of units from radius.  The circumference and radius of a circle are different quantities that are related by a formula; it is not a "change of units", but rather translation to a different quantity that describes the same phenomenon (the "size" of a circle, in this instance).  The same applies to "wavevector" and "angular-wavenumber vector": this are different quantities, and hence must not be confused.  You say that "wavevector" rather than "angular-wavenumber vector" is the primary concept; this makes the case for some way of clarifying that the latter is meant (as may be figured out from the context), so we should not just give a link to "wavevector" without disambiguation.  My choice might not be great, but that is because WP has not found a suitable distinct term yet; I just used the term given in the lead of that article.  Which is to some extent the result of a campaign to conflate/merge homonyms from different disciplines in WP.
 * As a concrete point: do you have a suggestion for linking "wavevector" in such a way that it is clear that "angular-wavenumber vector" is meant rather than just the primary meaning of "wavevector"? —Quondum 13:19, 20 May 2023 (UTC)
 * If I understand correctly, rather than "angular units confusion" the issue is "misapplication of wavevector concept"?
 * Can you point me to an example of "wavevector" and of "angular-wavenumber vector"? Johnjbarton (talk) 14:35, 20 May 2023 (UTC)
 * Maybe I should step off my soapbox for a second, and focus on this article. In my change, linked (Special:Diff/1155722477) in the opening post of this thread, I made the change "wave vector" → "angular wave vector", since the former, interpreted as ISO 80000-3:2109 defines it (no other redefinition is given in the text), makes the given equation incorrect.  We need disambiguation in the article of some sort.  You don't seem to like the term that I used; do you have a suggestion?  —Quondum 17:23, 20 May 2023 (UTC)
 * I think that the article Dimensionless units in the SI gives an important clue:
 * Another quantity associated with waves is the wave vector � k = 1 . (24) It has units of radians per meter or rad m−1. (The magnitude of the wave vector is to be distinguished from the wavenumber λ−1 used in spectroscopy.)
 * This connects to the entries 3.20 and 3.21 in the ISO table.
 * So it seems that "angular wavevector" isn't used even when the units are radians per meter.
 * I picked up four classic textbooks and could not find "angular wavevector".
 * Perhaps that is the logical term but I think we should find some uses. Johnjbarton (talk) 03:07, 21 May 2023 (UTC)
 * Folks, I wonder how critical this is. I believe it is a little more complex than much of the description so far. The article wavevector kind of explains it, but I don't think it is clear. My attempt.
 * Physics convention is to use $$\exp(i\bf k.r)$$ for a plane wave, with $$\bf k$$ the wavevector. Crystallograpy uses $$\exp(2 \pi i\bf k.r)$$. Because of this the reciprocal lattice vectors differ, those in the physics notation being $$2\pi$$ larger. Other things such as the Ewald sphere can be subtly different, and also Fresnel propagators, Fourier transforms etc.
 * The wavevector page was IMHO influenced by crystallographers, as it reserves the use of wavevector for the crystallography convention. Although I am 50% a crystallographers, I don't support that view. I would ignore the ISO recommendations, mention that this page follows the physics convention and move on. Ldm1954 (talk) 04:08, 21 May 2023 (UTC)
 * As an encyclopedia I think we should reflect that scientist sometimes use "wavevector" to mean two things (as wavevector does with possible additions) but we should not introduce "angular wavevector", no matter how logical unless we have some citable evidence. Personally I would be ok with discussion on the wavevector page to the effect that "angular wavevector" could be more consistent but that the term isn't used in practice. Elsewhere just "wavevector" linked to the wavevector page.
 * To be sure: the sections containing these two words have many more important issues. Too much material is repeated, the order is inconsistent, citations are missing, speculative work is given too much weight. Johnjbarton (talk) 16:05, 21 May 2023 (UTC)
 * One thing we definitely shouldn't do is introduce new terminology, even if we find it logical. We can explain the different conventions in different fields and then pick one to stick with. The citation to Wang (2016) looks like a distraction &mdash; one person's obscure proposal, being given equal weight to the basic statement in every textbook. XOR&#39;easter (talk) 17:52, 23 May 2023 (UTC)

I believe calling k an angular vector is incorrect, sorry.Ldm1954 (talk) 20:52, 20 May 2023 (UTC)
 * This is not helpful. I don't care what we call it: I am open to suggestions.  You seem to have completely missed the point that to a reader of this article "wave vector" is ill-defined: the meaning of the term clearly depends on the context, and this article does not say which.  We need to disambiguate this somehow.  (The article Wave vector distinguishes between two distinct concepts, and chooses different terms to avoid confusing the two.  Do not use it as guidance on terminology.)  Watch out to avoid falling into the trap of thinking in terms of terminology rather than in terms of concepts.  —Quondum 16:16, 21 May 2023 (UTC)
 * Sorry, I do not agree with you and the majority of the physics and crystallography communities will not either. It is a vector in reciprocal space, and we should stay with convention. As one example, X-ray crystallography defines it as a position in reciprocal space, similarly in Ewald's sphere.Ldm1954 (talk) 16:25, 21 May 2023 (UTC)
 * I feel like I am speaking through a broken telephone. You are either refusing or simply failing to understand the point that I am making.  You are also failing to communicate clearly.  What point do you disagree with?  The use of a particular term?  Or that the term "wave vector" (or "wavevector") gets used with different meanings in different contexts?  You have not acknowledged that the only international standard that apparently defines the term defines it in an incompatible way to that at Reciprocal lattice.  Please don't take the perspective of "I am right, you are wrong"; if you wish to be collaborative, find a basis for common understanding; acknowledge the point made by others, and build a shared understanding.  As I have pointed out, this is not about correct terminology, but helping the reader understand without confusion.  —Quondum 16:51, 21 May 2023 (UTC)

Do quasiparticles belong here?
I am raising this for consideration. Phonons for instance don't, but holes in semiconductors might. Currently everything is for matter waves in vacuum, but that is not everything.

Related to this current flow could also be worth mentioning rather than just the group velocity.

N.B., I think the improvements are noticeable, but some more remains. Ldm1954 (talk) 03:37, 22 May 2023 (UTC)


 * Addendum to my own question. I propose an additional section on "More complicated matter waves". Within this would be parts of the quasiparticle link, specifically electrons in a solid, hole, some polariton, Cooper pairs, Bloch function (they arise in electron diffraction), electron vortex (newer area in electron microscopy) Exciton. More a list with refs and redirects. Ldm1954 (talk) 15:12, 23 May 2023 (UTC)
 * How about "Multiparticle matter waves" "Multiparticle matter wave states" "Quasiparticle matter waves" "Collective-matter waves" "Multiparticle excitations as matter waves" "Excitations in solids at matter waves"?
 * The "list with redirects" would fit will with my ongoing "Applications" section which would have a similar flavor. Johnjbarton (talk) 15:53, 23 May 2023 (UTC)
 * Not quite. For instance an electron vortex beam a Bloch wave are single-particle. (There is some info out there about atom/ion vortex and neutron vortex, e.g. https://arxiv.org/pdf/2104.14619 & https://www.birs.ca/workshops/2017/17w5079/files/BabikerBIRSApril2017.pdf; I have not checked to see what is real or ready to include here.)
 * I would make two sections, "Single matter wave states" (or similar) and "Collective-matter waves". Reflecting we should differentiate them. The ideas of group velocity, probability flow, effective mass would be for the first; then just say also for the collective waves. Ldm1954 (talk) 16:13, 23 May 2023 (UTC)
 * "Single matter wave states"? That means what?  Perhaps you mean "Single-particle matter wave states"?  —Quondum 17:51, 23 May 2023 (UTC)

Draft of proposed new section "Application of Matter Waves"
Please review Applications of Matter Waves for inclusion in this page. You can comment by reply or simply edit the content.

A lot of material is not represented yet, but much of that needs to be included in pages that will then be linked here. And some of those pages -- Atom optics I'm looking a you -- need quite a bit of work first. Rather than bulk up a generic topic like Matter Wave with specifics I think a better strategy is to fix of the specific pages and expand this list of links. Johnjbarton (talk) 04:00, 25 May 2023 (UTC)


 * Yes, and it would include the Atoms, Neutrons & Molecules part.
 * However I think a few things should be done first.
 * One is the last section whose relevance I don't understand. To me the elements of that which are kept go earlier into the History.
 * A second is the long section on De Broglie relationships. To me someone may not know the relevance. I think it needs more wordsmithing.
 * Figures. I am used to a Figure every 1-2 pages. Currently it is 9 pdf pages +refs, and 2 Figs. (I am not a big fan of the first Figure as nowhere else are wavepackets mentioned.)
 * And, as you said, other pages need some TLC. Ldm1954 (talk) 13:44, 25 May 2023 (UTC)
 * Last section: I moved the first and third (last) paragraphs into History and deleted the section. Note that this section was discussed on another topic and others also thought it was not useful.
 * My version of de Broglie's hypothesis is a bit longer and more mathy than what we had before. It follows his historical derivation and attempts to connect it to modern forms without the calculus parts.
 * It turns out that other pages ref this section as the "de Broglie hypothesis". Johnjbarton (talk) 16:43, 25 May 2023 (UTC)
 * De Broglie relationships: Sorry I won't be able to help with this, I don't get what that section accomplishes. Johnjbarton (talk) 17:14, 25 May 2023 (UTC)
 * Also, I think a section is needed on the transition from quantum to classical. Exactly how we decide to describe this can be discussed further. One is incoherence (laser versus light bulb), but there can be others. Ldm1954 (talk) 14:57, 25 May 2023 (UTC)
 * Yes I agree, but I'm unsure why all of these issues need to precede adding Applications. Johnjbarton (talk) 16:46, 25 May 2023 (UTC)
 * It is more to finalize what is there before adding more. Just my approach, step-wise.
 * Back to the wonders of preparing pptx for a class and writing reports... Ldm1954 (talk) 17:07, 25 May 2023 (UTC)
 * I added the new section, some history relate to atoms, and cleaned up the History section.
 * Started a new topic TODOs. Johnjbarton (talk) 03:46, 29 May 2023 (UTC)
 * I like the concept, but I would move it to the end. I would also suggest moving the neutron/atom part from earlier, as it was already proved. See also ToDo. Ldm1954 (talk) 12:43, 29 May 2023 (UTC)
 * Moved Applications to the end. Declaring victory on this item.  See TODOs.
 * Johnjbarton (talk) 19:40, 29 May 2023 (UTC)

The statement "... but the wavelengths are all in the picometre range, comparable to atomic spacing. (Atomic diameters range from 62 to 520 pm, and the typical length of a carbon–carbon single bond is 154 pm.)" leaves the reader wondering, and so should be clarified. I can deduce that the entries are in the table as a result of probing atomic wavelengths only being done through diffraction by atomic lattices, but this should be made clearer for the reader. It also suggests the question: why are matter waves not diffracted off say an optical lattice or materials with a larger spatial period, which might permit probing a very different range of wavelengths? —Quondum 00:40, 30 May 2023 (UTC)


 * The most common use is for the spacings in the table. Of course there are also diffraction phenomena at much larger spatial periods, and transverse coherence lengths can be microns.
 * I think that section is a good start, and needs expansion/work. Ldm1954 (talk) 00:50, 30 May 2023 (UTC)
 * Thanks, I made an attempt to clarify that the range is mostly limited by technology.
 * We could call out the extremes with references. 2pm is close to the limit of measurement, used in the molecule cases. We could probably find an electron application below 54eV. Johnjbarton (talk) 01:55, 30 May 2023 (UTC)

A dubious but rare figure.
The de Broglie hypothesis section contains this figure:

Sadly, as we have few figures, I think this one is a bit off the mark, at least as captioned.

The top image may be ok as a plane wave, but at least we need to change "spread out like a waveform" -> "spread out over all space".

The bottom image claims to be a wave packet. That's fine but it is "seductive": it leads reader toward particle-wavey things that are fundamentally dynamic.

I propose to cut out the bottom and alter the caption.

I know that @Ldm1954 complained about it as well, maybe on different grounds IDK. Johnjbarton (talk) 03:09, 2 June 2023 (UTC)

TODOs
TODOs:

1) Comparison of matter wave and light wave (same eqn for free particles, vastly different dispersion)

2) Transition to classical.

3) Coherence.

4) De Broglie relations. 5) Figures

A not-deeply-technical section on the first three combined might work.

I could add a history paragraph on C. Darwin's wave packet paper. Would connect to dispersion. Then we could copy a figure from wave packet. Johnjbarton (talk) 03:47, 29 May 2023 (UTC)


 * Did the Darwin add to history; please take a look. Johnjbarton (talk) 04:24, 29 May 2023 (UTC)
 * I suggest that the "De Broglie relationships" gets changed to "Travelling matter waves forms". I feel the "Travelling" part matters; the rest can be adjusted. These would be defined as those with a non-zero group velocity, better probability flux. The term could be used elsewhere.
 * There can then be a section on "Standing matter waves". All time independent have a $$E/ \hbar$$ term.
 * I would not combine light with 2) & 3). I think the latter are critical, and need a few paragraphs. Ldm1954 (talk) 12:54, 29 May 2023 (UTC)
 * Ok I did a "Traveling wave" thing. I reordered and cleaned up the subsections. I think it's better. Johnjbarton (talk) 19:39, 29 May 2023 (UTC)
 * I reworked the group and phase velocity sections. This version is less like a tautological proof that v_g=v (de Broglie assumed as much) and more simply giving the velocity formula and the relation v_g*v_p=c^2.
 * I left the two bits of each section but I'm not happy with them.
 * Separately I have worked on the matter wave dispersion relations as linked in this new version.
 * Please check. Johnjbarton (talk) 16:57, 1 June 2023 (UTC)
 * Looks good. However, remember that WP is not a reliable source, so other sources are needed, not just links. A pain, but someone may hack the link so... Ldm1954 (talk) 02:15, 2 June 2023 (UTC)

Proposed new section: Special relativity and de Broglie's phase harmony
Some time back we deleted a section we did not understand. It concerned me that that it quoted de Broglie's thesis.

While working on the phase velocity section I read more of de Broglie's original work. His famous work includes a simple but consequential application of special relativity. To me the combination of wave-particle QM and special relativity in a historical context is simply too notable and appropriate for reader of Wikipedia Physics to let go.

I have resurrected the section in spirit but completely re-wrote it and built a figure to aid in understanding.

I am looking for feed back. I've already decided to add a light grey x-axis. Other suggestions on the figure welcome before I go through the tedious edit cycle for it.

My goal for this section would be that someone with a little understanding of relativity and a little of wave-particle duality would come away knowing that these are, surprise!, deeply connected. Johnjbarton (talk) 23:15, 6 June 2023 (UTC)


 * The intuition behind de Broglie's insight seems to be straightforward (as from the originally deleted section that you linked). The animation in your sandbox does not help (at least, it is opaque to me).  I also find the new wording obscures insight.  Here is how I think of it: when the observer is in the particle's rest frame, there is a phase that is the same everywhere but linearly increasing with time (though the amplitude might be localized, e.g. in a Gaussian spatial distribution).  In a Galilean framework, a moving observer would see everything still in phase everywhere, just with the distribution peak moving (the original observer's axis on which his origin moves, i.e. his time axis, is just tilted).  In special relativity, the time axis also tilts, but the plane of t = 0 also tilts by the same amount, with an associated squeeze transformation at 45°.  The moving observer's t = 0 plane now cuts through the planes of constant phase, producing spatial oscillations (nonzero wavevector).  A simple space–time diagram wit these two conditions next to each other would be able to illustrate this easily.  No need for any formulae.  —Quondum 00:01, 7 June 2023 (UTC)
 * While an alternative point of view is an interesting topic, my goal was only to report de Broglie's point of view in a way that can be related to other wikipedia articles. Obviously that was not successful. Johnjbarton (talk) 02:21, 7 June 2023 (UTC)
 * Since I have not done any hard-core relativity since undergrad, I honestly have no clean idea what either of you are referring to -- which suggests that a better explanation is needed of the relevance. (I assume that there is something more than the existing 4-vector representation.)
 * N.B., it may be that this connects to relativistic inelastic scattering and Cherenkov and similar, but now I am speculating. Ldm1954 (talk) 02:39, 7 June 2023 (UTC)
 * This is just a 4-covector. In special relativity, a scalar function of spacetime $ψ(x^{ν}) = exp(iωt)$ [where $ω$ is a constant, $t = x^{0}$, and $x^{ν}$ is the 4-position] necessarily takes the form $ψ(x^{ν}) = exp(ik_{μ}x^{μ})$ for a constant 4-covector $k_{μ}$.  This is a direct directly fits "by cause of a meta law of Nature, to each portion of energy with a proper mass $m_{0}$, one may associate a periodic phenomenon of frequency $&nu;_{0}$", with a modern restatement de Broglie's subsequent wording.  —Quondum 11:02, 7 June 2023 (UTC)
 * What you say may be perfectly valid but there's too many unconnected dots for me. I don't think "just a 4 co-vector" will work for many readers, even if it is correct and minimal. Johnjbarton (talk) 16:50, 7 June 2023 (UTC)
 * Your comment reinforces my sense that we should do something to clarify that matter waves are a direct consequence of special relativity. @Quondum implies this is common (physics) knowledge, but I only came across the connection in the context of editing this page.
 * To be clear, this is not a 'relativistic effect' in the normal sense of $$ v\rightarrow c$$. Rather, the de Broglie wavelength does not manifest at all unless there is some relative velocity.
 * Rehashing de Broglie's (rather lame) arguments may not be the best way to accomplish this, but I do not have access to better citable alternatives. What might the matter wave be telling us of the nature of matter? covers the topic with many citations to others, but I don't think it reaches the bar for citation. Johnjbarton (talk) 16:43, 7 June 2023 (UTC)
 * To me matter waves come from QM. I don't think QM comes from special relativity. Also, a particle in a box has a wavevector but no group velocity or probability flux (standing wave). If I remember his thesis right, de Broglie was also thinking about standing waves. Ldm1954 (talk) 16:50, 7 June 2023 (UTC)
 * It's 'just' the (observed) wavelength that comes from relativity. A stationary matter wave has no wavelength (or the wavelength approaches infinity). The phase is just rotating at the same value in all space. With motion the observed phase varies with space, the variation depending on relative velocity. It's both profound and trivial. For example, the phase of a particle stationary with respect to a detector has no consequence AFAIK. Johnjbarton (talk) 17:26, 7 June 2023 (UTC)
 * A matter waves cos(2\pi k.r -E*t/hbar) has a wavevector k, a wavelength 1/|k|, time dependence and no probability flux. A matter waves exp(2\pi ik.r - qz) is evanescent along z with no probability flux in z, only x and y. Currently there is not (IMHO) adequate coverage here of anything beyond fully travelling waves. Ldm1954 (talk) 17:40, 7 June 2023 (UTC)
 * Even the link above given by Johnjbarton, despite giving a reasonable analysis and insight, devolves into formulae with gammas and so on, which is not likely to impart insight to the average physics-oriented reader. But it does seem to think that de Broglie was not able to think holistically about this idea, so for the purposes of the article, such an insight would have to be presented as subsequent development of de Broglie's conception.  The confined scalar wave $R(r) exp(iωt))$ [r being time-independent on the stationary observer's frame] has the potential of being simple to present and demystifies the phase and travelling velocities without needing gammas to present.  This is valuable to a reader and clearly referenced, but I leave it to you decide whether/where it belongs in this context.  —Quondum 11:47, 8 June 2023 (UTC)
 * Yes that is also my assessment: pluses and minuses. The Shanahan article amounts to (re)-interpretation: very interesting but at the current stage it does not predict results that can be verified. For now I think set this aside until I can read more. Johnjbarton (talk) 16:43, 9 June 2023 (UTC)

Standing matter waves
Thinking of standing matter waves as a separate class seems to me to be erroneous. That would be saying that the standing modes of an electromagnetic wave form a separate class, whereas it is simply an emergent phenomenon given boundary conditions imposed on a travelling wave: it is just a superposition of travelling waves. In this context, multi-particle waves do not appear to behave as a superposition: the wavevector is determined by the total mass (or perhaps a more complex description). —Quondum 12:53, 8 June 2023 (UTC)


 * Also, the connection between the effective mass for standing and travelling matter waves is the same in all cases -- via the second derivative, it does not matter whether they are quasiparticles or not. Ldm1954 (talk) 02:33, 9 June 2023 (UTC)
 * May I suggest that standing matter waves are not analogous to electromagnetic standing modes? AFAIK the latter are purely different boundary conditions. But standing matter waves are idealized models for bound quantum systems where forces alter the waves rather than boundary conditions. We talk about "particle in a box" not in comparison to blackbody radiation but in comparison to hydrogen.
 * In fact half of de Broglie's original punch was his application of waves to Bohr atoms. Turns out that his treatment did not make the cut, but it was a thing and lit a fire under Schrodinger.
 * To further this section we need to make contact with matter wave concepts in chemistry. Johnjbarton (talk) 16:54, 9 June 2023 (UTC)
 * Agreed, what I added was just a stub on that. Ldm1954 (talk) 16:57, 9 June 2023 (UTC)


 * Sorry, no, standing waves have zero probability flux (group velocity is a less accurate term), and as such are fundamentally different from travelling waves which have a probability flux. Indeed, de Broglie connected hydrogenic states to standing waves in a ring, without doing the detailed math.A case can be made that most eigensolutions such as hydrogenic are standing waves.

Ldm1954 (talk) 02:20, 9 June 2023 (UTC)


 * I'm sorry that I opened this discussion. I cannot work with this style of argument.  —Quondum 10:44, 9 June 2023 (UTC)
 * My apologies if I came across too strongly, but there are deep differences and this matters. Probably overkill, oversimple:
 * A travelling matter waves is going from A to B; a standing wave such as a particle in a box is not moving. Both have energy, effective mass and wavelength. Both are eigensolutions for different classes of problems, one free and the other with extra conditions.
 * For a free travelling matter waves, exponential, one can superimpose different wavevectors of the same modulus -- this is what one has in matter wave elastic diffraction. One can consider the small probe formed in scanning systems as an emergent phenomenon, as it comes from combining many waves. For a matter waves in a box you have to use cos/sin terms, you cannot separate the exponentials -- it is not emergent. Ldm1954 (talk) 12:39, 9 June 2023 (UTC)


 * My purpose with this thread was not to trigger a debate. Reconciling our perspectives would be nontrivial.  —Quondum 13:19, 9 June 2023 (UTC)