Wikipedia talk:WikiProject Physics/Archive April 2023

Notice of Fringe Theories Noticeboard discussion
There is currently a discussion at Fringe theories/Noticeboard regarding an issue with which you may have been involved. The discussion is about the topic Dark energy. Thank you. –LaundryPizza03 ( d c̄ ) 20:14, 3 April 2023 (UTC)

Minor image caption query
The caption of File:Asymmetricwave2.png reads
 * "Asymmetric wavefunction for a (fermionic) 2-particle state in an infinite square well potential. The 3D graph show the wavefunction for the 2-particle fermionic first excited state for the one dimensional infinite square well."

The reference to "one dimensional" is confusing, and the author has not edited in a while. Should I change this to "two-dimensional", as my intuition tells me? —Quondum 12:23, 4 April 2023 (UTC)
 * Not necessarily. I think the caption might be right, the potential is 1D and the plot axes are wavefunction vs the 1D coordinates of each particle.--ReyHahn (talk) 13:56, 4 April 2023 (UTC)
 * Ah, thanks. That gives the background that I was needing.  I'll need to think how to adapt the caption to make this clear (though don't let that stop anyone pre-empting me).  —Quondum 14:08, 4 April 2023 (UTC)
 * This is correct. If you look at the code on page File:Asymmetricwave2.png you can see it is indeed a Slater determinant $$\Psi({x}_1, {x}_2) = \chi_1(x_1) \chi_2(x_2)-\chi_1(x_2) \chi_2(x_1)$$ for the two lowest states. Jähmefyysikko (talk) 14:11, 4 April 2023 (UTC)
 * Changed: diff at Electron. —Quondum 14:24, 4 April 2023 (UTC)
 * Also, the caption on the file now reads
 * "Asymmetric wavefunction for a (fermionic) 2-particle state in a one-dimensional square well potential of infinite depth. The 3D graph shows the wavefunction for the 2-particle fermionic first excited state for the square well, with each horizontal axis giving one particle's position."
 * —Quondum 14:27, 4 April 2023 (UTC)

Good article reassessment for Astronomy
Astronomy has been nominated for a good article reassessment. If you are interested in the discussion, please participate by adding your comments to the reassessment page. If concerns are not addressed during the review period, the good article status may be removed from the article. Onegreatjoke (talk) 22:41, 15 February 2023 (UTC)


 * This was put on hold but will be reopened tomorrow. XOR&#39;easter (talk) 17:20, 13 March 2023 (UTC)
 * This article still needs some referencing and/or rewriting generalities for greater precision. XOR&#39;easter (talk) 14:37, 25 March 2023 (UTC)
 * After some pruning and cleanup (turning a list to prose, etc.), it's down to 3 citation needed tags. XOR&#39;easter (talk) 15:33, 1 April 2023 (UTC)
 * Now down to 2. XOR&#39;easter (talk) 15:49, 10 April 2023 (UTC)

Project-independent quality assessments
Quality assessments by Wikipedia editors rate articles in terms of completeness, organization, prose quality, sourcing, etc. Most wikiprojects follow the general guidelines at Content assessment, but some have specialized assessment guidelines. A recent Village pump proposal was approved and has been implemented to add a class parameter to WikiProject banner shell, which can display a general quality assessment for an article, and to let project banner templates "inherit" this assessment.

No action is required if your wikiproject follows the standard assessment approach. Over time, quality assessments will be migrated up to WikiProject banner shell, and your project banner will automatically "inherit" any changes to the general assessments for the purpose of assigning categories.

However, if your project has decided to "opt out" and follow a non-standard quality assessment approach, all you have to do is modify your wikiproject banner template to pass WPBannerMeta a new custom parameter. If this is done, changes to the general quality assessment will be ignored, and your project-level assessment will be displayed and used to create categories, as at present. Aymatth2 (talk) 20:44, 12 April 2023 (UTC)

Talk:Rayleigh–Jeans_law
More eyes here would be appreciated. This is similar to Wikipedia talk:WikiProject Physics/Archive_February_2023. &#32; Headbomb {t · c · p · b} 02:37, 9 March 2023 (UTC)


 * This indirectly led me to create Category:Old quantum theory, but then see Talk:Planck's law. XOR&#39;easter (talk) 16:20, 14 March 2023 (UTC)


 * This discussion is getting highly frustrating. If other people with a clue could chip in, that would be much appreciated. &#32; Headbomb {t · c · p · b} 01:09, 16 March 2023 (UTC)
 * I've noticed that in addition to Rayleigh–Jeans law, we have Planck's law, black body, black-body radiation, Wien approximation, and Wien's displacement law. I don't know the best way to organize this topic, but I'm pretty sure that that's too many articles. Do we really need a page for the left side of the Planck curve, the right side of the Planck curve, and the location of the peak in between? In addition to being difficult to maintain, this scattershot approach seems more like a dictionary of physics than an encyclopedia. XOR&#39;easter (talk) 13:39, 16 March 2023 (UTC)


 * In addition to the above, there is also an article for the Ultraviolet catastrophe, which to me seems to belong together with the Rayleigh-Jeans law. And then there's the Stefan–Boltzmann law, which is basically the integral of Planck's law (but it can also be derived independently of it from thermodynamics). The Stefan–Boltzmann constant also has its own page. --Jähmefyysikko (talk) 14:50, 16 March 2023 (UTC)


 * It certainly seems to make sense to combine most of these. Most of them have the flavour of being sections or historical context for a fuller description.  Black body might be better kept separate.  —Quondum 15:25, 16 March 2023 (UTC)
 * I'd say merge Stefan–Boltzmann constant into Stefan–Boltzmann law, and also combine Ultraviolet catastrophe, Rayleigh–Jeans law, and Wien approximation into Planck's law (at the very least). XOR&#39;easter (talk) 17:12, 16 March 2023 (UTC)
 * While we are it, consider also merging Curie constant into Curie's law.--ReyHahn (talk) 20:57, 16 March 2023 (UTC)
 * Good idea. XOR&#39;easter (talk) 22:17, 16 March 2023 (UTC)


 * One might also consider merging Black body radiation with Planck's law. Some parts of that article might be combined with the Black body. Apart from merging, it might also be useful to have the History section of Planck's law as a standalone article. It certainly looks long enough, and could then be reused in other articles with . Currently the history is also scattered across the wiki pages, and it is difficult to find a well written account. --Jähmefyysikko (talk) 14:16, 17 March 2023 (UTC)
 * I was thinking along similar lines about merging black body radiation with Planck's law and trying to reduce redundancy between those and black body. I was also contemplating whether we should split off the "History" section of Planck's law, particularly if we're merging other stuff into it. Arguably, the encyclopedic topic is the origin of quantum mechanics; this was all happening simultaneously with trying to understand atomic structure, the photoelectric effect, the mechanism behind spectra, the specific heats of gases, etc. Maybe it belongs in History of quantum mechanics, which is rather an unloved-looking article. XOR&#39;easter (talk) 14:42, 17 March 2023 (UTC)
 * Oh, there's thermal radiation, too. XOR&#39;easter (talk) 16:21, 19 March 2023 (UTC)
 * What's the problem with thermal radiation? it is clearly about real thermal radiation and not the one that is described by Planck's law or a blackbody. Also near field effects.--ReyHahn (talk) 16:23, 19 March 2023 (UTC)
 * Yes, it's more broad in scope. I just mean that we ought to consider it as well if we're going to be reorganizing the content in this area. Some things could be merged into it, potentially, and some stuff could be taken out of it, and we should check it for historical accuracy. XOR&#39;easter (talk) 16:35, 19 March 2023 (UTC)
 * The thing with laws etc... is that they're all notable on their own right, and their derivations make assumptions that are historically important. These are best treated in individual articles, and not in one mega article dealing with thermal/blackbody radiation or whatever. I'm fine with the mega-articles existing, but they should point to the subtopics with Main when appropriate. &#32; Headbomb {t · c · p · b} 16:44, 19 March 2023 (UTC)
 * I think that's true sometimes, but not always. The history of different approximations can be all tangled up together, making them easier to explain jointly. Some divisions may make sense, but we've gone too far in that direction. Like I said earlier, I don't know the best way to manage this corner of the encyclopedia, but I'm pretty darn sure that what we've got now isn't it. XOR&#39;easter (talk) 17:00, 19 March 2023 (UTC)
 * Merging the constants to their corresponding law IMO is a pretty good start. &#32; Headbomb {t · c · p · b} 17:38, 19 March 2023 (UTC)
 * Agreed on the merging of constants (a section under an article on a law that defines them) is where they kinda belong. I feel that approximations to a better theoretical description provide significant history and context to that corrected version.  When these became large enough to split out, a subtopic linked as Main would work, but Rayleigh–Jeans law and Wien approximation do not seem to meet this threshold, being little more than stubs.  —Quondum 00:30, 20 March 2023 (UTC)
 * I've gone ahead and merged Curie constant into Curie's law. XOR&#39;easter (talk) 19:18, 18 March 2023 (UTC)
 * Ultraviolet catastrophe, Rayleigh–Jeans law, and Wien approximation have been tagged for proposed merger into Planck's law, with reference to this discussion thread. –LaundryPizza03 ( d c̄ ) 05:43, 26 March 2023 (UTC)
 * I disagree with incorporating these three into Planck's law. They precede Planck's law and were not derived from it. They should/could be expanded with their proper derivations, which should not be included in the Planck's law article. These articles could be combined into black body radiation, along with an introduction to Planck's law, with Planck's law remaining as a separate article as the most accurate theory. These distinct laws all have thousands of readers and are well-known. I wouldn't want to be dropped into Planck's law, which is already huge and messy, if I was just looking for a reminder of what Rayleigh-Jeans or Wien's laws were.
 * UV catastrophe merged with Rayleigh-Jeans law should be fine. Ponor (talk) 11:31, 16 April 2023 (UTC)

Good article reassessment for Albert Einstein
Albert Einstein has been nominated for a good article reassessment. If you are interested in the discussion, please participate by adding your comments to the reassessment page. If concerns are not addressed during the review period, the good article status may be removed from the article. AirshipJungleman29 (talk) 23:01, 17 April 2023 (UTC)

Bloch theorem size effects
I renamed a section in Bloch theorem, called A relevant new theory into Size effects. It seems that it wants to discuss the problems of modelling crystalline solids when there are boundaries or low dimensional effects, however the section is so vague that it is unclear to me if it is relevant or not. Can somebody take a look? ReyHahn (talk) 15:14, 18 April 2023 (UTC)


 * Bloch theorem treats a crystal of infinite size with no boundary. On the other hand, a genuine crystal always has a boundary and a finite size. The simplest model which can treat both the boundary and the size effects is the Particle in a box model with a periodic potential. The new theory is such a model thanks to recent progress in the mathematical theory of periodic differential equations. Bloch theorem does not have size effects. The new theory contains both the boundary and the size effects. Luman2009 (talk) 23:44, 19 April 2023 (UTC)


 * Unfortunately, the section  is just interpretive waffle: 's summary here is a precis of its information content. It reads like a suggestion to go and check out the work by one author, without giving usable concrete information.  As it stands, IMO it is unencyclopedic and the section should be deleted.  It may take an expert on the topic to produce an encyclopedic outline of what the referenced papers say.  —Quondum 12:53, 20 April 2023 (UTC)
 * I agree with you . You cannot just say this theorem has problems, "there are novel ways", without providing key words of what these actual new formalisms are. This is maybe strawmanning but imagine going into the blackbody radiation article and you have a whole section saying "we cannot explain blackbody radiation using 1900 physics, because of ultraviolet divergences, but there are novel ways [1]", where [1] Planck 1900. I suggest deletion too. --ReyHahn (talk) 15:07, 20 April 2023 (UTC)
 * Did you see "A more general model: particle in a box with a period potential in Particle in a box" at the end of the first paragraph of the section? It already has the more usable concrete information you questioned and appeared on Wikipedia earlier. I tried to avoid repeating those, so more interpretive contents in the article Bloch theorem.
 * I am also working on a draft, "Quantum confinement of Bloch waves." It has more detailed information about the background, the approach, the conclusions, and the consequences of the new theory. You are welcome to come to my Sandbox to look at the draft. I will appreciate your further comments. Luman2009 (talk) 16:12, 20 April 2023 (UTC)
 * I am not at all convinced that a multiple-paragraph section on this is warranted by the available sourcing. (As written, it is also quite vague.) An article like Bloch's theorem should be mostly or entirely standard material for condensed-matter physics. XOR&#39;easter (talk) 19:26, 20 April 2023 (UTC)
 * The fact that you and we keep referring to the method as the "new theory" means that it not well established enough to have its own name in popular physics knowledge. I will proceed with deletion of the section until the draft is validated and this problem is clarified.--ReyHahn (talk) 11:56, 21 April 2023 (UTC)
 * I don't think the existence of a name is a good criterion for inclusion. Possibly a one sentence mention in the article that "in xxx, author xxx proposed an extension of Bloch theorem" would suffice, and/or a see also link to Luman's draft, when it is finished. Fermiboson (talk) 17:55, 24 April 2023 (UTC)
 * The now-removed section was based entirely on primary sources, which strictly speaking aren't what we should use even for a single-sentence mention. The draft, as it currently stands, still has problems of that nature. It takes some publications that seem to have only ever been of niche interest and essentially talks them up as being a great advance. XOR&#39;easter (talk) 20:58, 24 April 2023 (UTC)
 * I agree, in its current state. I'll spend some time and see if I can make it better. Fermiboson (talk) 21:02, 24 April 2023 (UTC)
 * By the end, it spills over into saying that the condensed-matter physics community is thinking about basic things in the wrong way. This raises NPOV concerns, to put it mildly. It's not Wikipedia's job to evaluate such claims or provide a soapbox from which to make them. XOR&#39;easter (talk) 21:02, 24 April 2023 (UTC)
 * Absolutely. I do feel there is sufficient value in it to make a short article, however. None of the "most important theorem" wording would stay obviously. Fermiboson (talk) 21:04, 24 April 2023 (UTC)

Probability current
The extra term $$\frac{\mu_S}{s}\nabla\times(\Psi^* \mathbf{S}\Psi) $$ cannot be correct in SI-units since the probability current density j has the units $$\mathrm{s}^{-1}\mathrm{m}^{-2}$$ whereas the magnetic moment has the unit $$\mathrm{A m}^2$$. And $$\frac{\mu_S c}{s}\nabla\times(\Psi^* \mathbf{S}\Psi)$$ cannot be correct in Gaussian units either. FbiSupLabAcc (talk) 05:33, 25 April 2023 (UTC)
 * For electrons it should read $$\frac{\mu_{\rm B}}{\hbar e}\nabla\times(\Psi^* \mathbf{S}\Psi) $$ does that help? --ReyHahn (talk) 17:12, 25 April 2023 (UTC)
 * I was thinking that it looked bereft of an $$\hbar$$ and a charge somewhere. XOR&#39;easter (talk) 17:28, 25 April 2023 (UTC)
 * So the more general extra term in the article would lack the charge q and the "s" could/should be interpreterted as a "full" spin angular momentum $$s=\hbar/2$$ and not only as the usual notation s=1/2. So the extra term would read: $$\frac{\mu_S}{e\cdot s \cdot\hbar}\nabla\times(\Psi^* \mathbf{S}\Psi) $$ (with the usual s). In the case of the electron both candidates for the extra term would differ by a factor of 2 since µ_S is approx. µ_B and s=1/2. --FbiSupLabAcc (talk) 21:48, 25 April 2023 (UTC)
 * Does anyone have access to the supposed source? A random "study guide" from 2006 isn't particularly easy to come by (my only option would actually be interlibrary loan). I am curious if it was transcribed incorrectly or what. Actually, I'd be vaguely surprised if an exam-prep guide had anything on a rather niche topic like this at all. XOR&#39;easter (talk) 16:39, 26 April 2023 (UTC)
 * Here's the relevant page from 1998 edition of the same book: https://archive.org/details/schaumsoutlineof00pele/page/155/mode/1up Jähmefyysikko (talk) 06:20, 27 April 2023 (UTC)
 * A 2006 edition is also available, but I did not yet manage to find the equation: https://archive.org/details/quantummechanics0000pele/mode/1up Jähmefyysikko (talk) 06:33, 27 April 2023 (UTC)
 * The best way to write it is without the $$\mu$$, as $$\frac{\hbar}{2m}\nabla\times(\Psi^* \sigma\Psi) $$.--ReyHahn (talk) 08:38, 27 April 2023 (UTC)
 * The formula is absent in the 2006 version of the Schaum notes. It would be better to use another source, however I only know derivations for spin-1/2, e.g. P.Strange Relativistic Quantum Mechanics pp124.--ReyHahn (talk) 13:50, 27 April 2023 (UTC)
 * Nothing says we have to include the result for arbitrary spin. If the references mostly specialize to spin-1/2 (I haven't had time to do a survey, but that seems likely overall), then arguably we should too. XOR&#39;easter (talk) 13:08, 28 April 2023 (UTC)
 * I did a partial survey, you can find many versions of the spin-1/2 case, like in: Sakurai Advanced Mechanics, Greiner Relativistic mechanics, and Bjorken&Drell. Most of the time in its relativistic formulation, look for Gordon decomposition.--ReyHahn (talk) 13:12, 28 April 2023 (UTC)