Wikipedia talk:WikiProject Physics/Archive April 2018

Active discussions

Draft:Universal topology

Will someone please review this draft? On first review it appears to be the author's own ideas (and therefore original research). Robert McClenon (talk) 03:04, 3 April 2018 (UTC)

Never mind. It is the same as the edit-warring at Spacetime topology and as Universal topology in physics. Robert McClenon (talk) 03:21, 3 April 2018 (UTC)

Debye model merge

A discussion is open about the merge of Debye frequency with Debye model, as the former is just a parameter that appears in the later. This merge proposal is open since November 2017 (Discuss it here). MaoGo (talk) 09:12, 3 April 2018 (UTC)

Electron liquid

Quick question, is this article (electron liquid) a thing?. None of the references have electron liquid written and it seems just a vague term between Fermi liquid and jellium. --MaoGo (talk) 13:49, 3 April 2018 (UTC)

For the references see the earlier editions: [1]. --MaoGo (talk) 13:55, 3 April 2018 (UTC)

Electron liquids and electron hydrodynamics in graphene exist as a topic these days: Superballistic flow of viscous electron fluid through graphene constrictions, Hydrodynamics of electrons in graphene, Fluid dynamics of electrons in graphene. But these seem different than what is described in that article. --Mark viking (talk) 22:01, 3 April 2018 (UTC)
It seems like a vague copy of the Jellium article. --MaoGo (talk) 07:18, 4 April 2018 (UTC)
@Mark viking: the links you provided seems to discuss Fermi liquids (at least is clear for the first and the last, not completely sure about 2). --MaoGo (talk) 08:11, 4 April 2018 (UTC)

A link to a DAB page

Dirac matter links to the DAB page Abelian. This is well out of my field; can any expert here correct the link? Thanks in advance. Narky Blert (talk) 10:25, 6 April 2018 (UTC)

Spacetime topology‎

I think there's something very wrong about the lead of Spacetime topology‎. And perhaps the recent edits should be reviewed as well. Could someone have a look at this? - DVdm (talk) 14:36, 2 April 2018 (UTC)

Looks like the recent changes have been reverted. Primefac (talk) 15:22, 2 April 2018 (UTC)
Yes, thanks for the purge, Purgy Purgatorio. Expect some resistance... - DVdm (talk) 15:26, 2 April 2018 (UTC)
My intention was to just set a bookmark which I estimated to be at a rational place there (see next thread?)), and I was aware of violating some eternal rule for the umpteenth time, but I am very glad if I were to do something useful. You were very welcome. Purgy (talk) 07:22, 3 April 2018 (UTC)
I've tried to provide the pseudo-science caution about ArbCom discretionary sanctions. This appears to be original research which, in the area of physics, is a form of pseudo-science. Robert McClenon (talk) 10:46, 3 April 2018 (UTC)
I'd be wary of calling this pseudoscience. This is mostly WP:OR/WP:SYNTH stuff, not aether quackery. Headbomb {t · c · p · b} 15:22, 3 April 2018 (UTC)
User:Headbomb - What is aether quackery in the twenty-first century? I know about the luminiferous aether in nineteenth-century physics as a hypothetical medium that carried light waves, and which was inconsistent with the Michelson-Morley experiment. I know that any disproved theory never completely goes away. (I suppose there are also papers on phlogiston.) Quacking actually is bragging, making a lot of duck-like noises about how good one's medical procedures or snake oils are. What is aether quackery? Robert McClenon (talk) 19:17, 3 April 2018 (UTC)
Quackery related to aether_theories. I suppose quackery mostly refers to medical frauds, so I guess I should have written crackpottery instead of quackery. The point is, spacetime topology isn't pseudoscience and wouldn't be covered by the Arbcom DS. Headbomb {t · c · p · b} 20:42, 3 April 2018 (UTC)
Right, but there was this lead containing the phrase "a duality of the two-sidedness of physical and virtual reality lies at the heart of all events as they are interrelate, opposite or contrary to one another, each dissolving into the other in alternating streams that operates a life of creation, generation, production, annihilation, or actions complementarily, reciprocally and interdependently.'" Arbcom stuff, I'd say. - DVdm (talk) 20:54, 3 April 2018 (UTC)
More meaningless drivel than ARBCOM worthy stuff, I feel. But whatever. Headbomb {t · c · p · b} 21:58, 3 April 2018 (UTC)
By ArbCom drivel is meant pseudo-scientific stuff, because ArbCom discretionary sanctions apply to pseudo-science. That lede sentence has a flavor to it similar to the social text hoax. It sounds like quantum mysticism, but with the emphasis on the mysticism, not on the quantum physics. Robert McClenon (talk) 22:52, 3 April 2018 (UTC)
Please do not sneer at phlogiston. I was taught about it at school in the 1960s (as a discredited theory, but nevertheless as an example of a theory which fell apart when confronted with observations). Narky Blert (talk) 02:51, 8 April 2018 (UTC)

Possible page adoption: International System of Electrical and Magnetic Units

Would this page International System of Electrical and Magnetic Units be relevant for adoption into the WikiProject Physics? Sdc870 (talk) 17:38, 10 April 2018 (UTC)

Duplicated topic: Yarkovsky effect

Hello. I came across two articles that seem to be a duplicate of the same subject: Yarkovsky effect, and Yarkovsky–O'Keefe–Radzievskii–Paddack effect. Are they different phenomena or should they be merged? Thanks. BatteryIncluded (talk) 18:33, 13 April 2018 (UTC)

They look like different phenomena: the Yarkovsky effect is about changes in the orbit of a rotating body, the YORP effect is about changes in the rotation of the body itself. --Mark viking (talk) 19:05, 13 April 2018 (UTC)

Ending the system of portals

Hello, there's a proposal to delete all Wikipedia portals. Please see the discussion here. --NaBUru38 (talk) 14:00, 14 April 2018 (UTC)

Ultrasoft radiation

Not a term in wide use it seems, going by the existence of only 399 results on Google, many of which are automatically generated from the Wikipedia article.

Unlike Hard radiation and Soft radiation, which refer to loose ends of a spectrum, this article gives a hard limit as if it had been declared definitively true by a major authority. Really, the only citation given for any of it is a now-dead URL from what seems to be a college professor, who disclaims his definition immediately with "It is convenient...".

I am not a physicist and would defer to one in deciding whether this should be RfD'd. But it really seems like a physicist would say so. Henstepl (talk) 03:27, 15 April 2018 (UTC)

The term (and natural variants like "ultrasoft X-rays") is fairly widely attested in the literature. I'd say the article needs clarification rather than deletion. XOR'easter (talk) 16:27, 15 April 2018 (UTC)

Subspace and blocks

I have been adding Wikilinks to the text in Density matrix renormalization group to enhance comprehensibility for those of us without physics degrees, but I’m stumped by subspace and blocks, both of which are disambiguation pages. I don’t know which of the articles listed in each would be the right one to link to. Can anyone help me out? Thanks in advance. — Gorthian (talk) 22:10, 16 April 2018 (UTC)

I think understanding DMRG without the benefit of physics training would be a real challenge. In DMRG, a subspace is a Hilbert subspace and linear subspace seems the best target I found. A block in DMRG terminology is just a subsystem. I think the figure helps make the notion of a block more clear here. I added subsystem and the wl to the article. --Mark viking (talk) 22:40, 16 April 2018 (UTC)

Deletion proposal for Electron liquid

Discuss at Wikipedia:Articles for deletion/Electron liquid. MaoGo (talk) 09:12, 16 April 2018 (UTC)

In particular the article for jellium needs to considered together with this. Mangoe (talk) 16:49, 16 April 2018 (UTC)
@Mangoe: Jellium is a pretty standard term. Take for example the Marder, Condensed Matter: [2]. --MaoGo (talk) 11:29, 17 April 2018 (UTC)

Do we need this article? "Classical and quantum conductivity"

Classical and quantum conductivity is very useless as it is. Some articles link to it as a curiosity, it is not a history article, and in the end it does not discuss the difference between quantum and classical models. Additionally it was created by a user who only contribution was to write the unformated version of the article. --MaoGo (talk) 15:26, 22 March 2018 (UTC)

Reads like a student essay. Agree that it could go. Xxanthippe (talk) 21:37, 22 March 2018 (UTC).
How should I proceed? must it be an admin that proposes the deletion discussion? --MaoGo (talk) 12:30, 23 March 2018 (UTC)
MaoGo, see WP:AFDHOWTO. As a note (it's kind of tucked in there) if you use Twinkle the technical side of a nomination (steps I/II/III) are done automatically). Primefac (talk) 12:38, 23 March 2018 (UTC)
Thank you. It is more complicated than what I thought. I will take my time to follow this procedure correctly.--MaoGo (talk) 13:11, 23 March 2018 (UTC)
Well, I guess that's why I pointed out the Twinkle usage. In the Twinkle menu you just choose "XFD" and fill in your rationale. It takes care of the rest. Primefac (talk) 13:40, 23 March 2018 (UTC)
(To turn on twinkle: Log in, go to "Preferences" (top right), then "Gadgets", then check the box for Twinkle. It shows up as a new menu near the search box labelled "TW". At least that's what happens on my computer.) — Preceding unsigned comment added by Sbyrnes321 (talkcontribs) 15:40, 23 March 2018 (UTC)
Oh I didn't know it was there. Thanks!--MaoGo (talk) 16:28, 23 March 2018 (UTC)

Wikipedia:Articles for deletion/Classical and quantum conductivity

It is done. Feel free to leave a comment. --MaoGo (talk) 16:46, 23 March 2018 (UTC)

So, do we have one for Quantum Conducts & one for Classical Conducts? Unable to locate the correct pages, as most are talking out of nowhere. Even unable to locate the correct page for 7 Chakras or the Energy Chakras of the Earth. Thanks Vishal Bakhai - Works 08:23, 18 April 2018 (UTC)
I don't quite get it. May you point to a specific article that could have such a disambiguation issue? --MaoGo (talk) 10:33, 18 April 2018 (UTC)

Electron positron pair production image

With this edit a new user Chriskb19 (talk · contribs) has replaced the image [3] of an alectron positron pair production in article Electron with a new image [4]. User had announced this 5 months ago on the talk page: [5]. I reverted the change for reasons explained in a note on my talk page ([6]). Can someone have a look at this? TIA. - DVdm (talk) 18:40, 16 April 2018 (UTC)

As it happens, I have a PhD in Particle Physics (Manchester 1983) and I did particle physics research up to 2000 with experiments at DESY, CERN and SLAC. As part of this, I was involved with electron-positron conversions from gamma rays produced by B* meson decays, exploiting their production with approximately zero opening angle.

You say you find the zero opening angle (theta) to be problematical. I refer you to the maths in the Pair Production article which shows that, with certain approximations, the solution for theta is exactly zero degrees. However energy and momentum cannot be conserved if the opening angle is exactly zero. (This explains why a photon cannot convert to an electron-positron pair spontaneously.) In order to conserve these quantities, some momentum must be transferred to another object - a nucleus or an atomic electron. This object gets a small kick, partly longitudinal and partly transverse to the direction of the photon. The electron-positron get a transverse kick. It is unlikely that the pair get half each so the electron and positron open up slightly. The angle is typically very small, as good as zero in most cases. To detect an electron-positron pair, a magnetic field is needed to separate the particles by bending one clockwise and the other anti-clockwise. By tracking back the two arcs, the production point can be calculated and the zero opening angle checked. In a bubble chamber an electron-positron pair looks like the Greek letter gamma which becomes a pair of circles or a pair of spirals. The simple diagram in the Pair Production does gives the wrong impression about the opening angle. I have considered changing this diagram but unlike my correct one, it is easier to see what is going on without expanding it. Chriskb19 (talk) 21:05, 16 April 2018 (UTC)

@Chriskb19: may you provide some references? --MaoGo (talk) 11:22, 17 April 2018 (UTC)
I am not sure whether you want a reference here or in the Electron article or the Pair Production article. My contribution to the Electron article is just a new figure which agrees with the result in the Pair Production article, which was derived from mathematics and Relativistic Kinematics rather than from a referenced source. My contribution here is a clarification that would not be found in a reference because an author would consider it straightforward and of little interest. Chriskb19 (talk) 19:26, 18 April 2018 (UTC)
@Chriskb19: Just trying to follow WP:MAINSTREAM and WP:VERIFY. An easier way to clear any dispute is to find a good source where it is pointed out what you say: that images similar to the original one in the article come from a misconception. Another way is to find a similar image in a book or educational publication. Both images are just illustrative and potentially wrong anyway, we know nuclear scattering is not about colliding "spheres". --MaoGo (talk) 10:34, 19 April 2018 (UTC)
I see that the change to the pair production figure has been reverted by @MaoGo: "until the dispute is settled". As far as I know, there is no dispute as user @DVdm: had a query and I provided a satisfactory response (that the new figure agrees with the maths in the Pair Production page unlike the previous figure). It is true that any subatomic quantum physics diagram is at best an approximation to the truth - the article on Pair Production points out that the treatment is semi-classical. Nevertheless the diagram that I have provided has fewer issues than the one it replaces and it well describes what is seen in experiments. I believe it should be accepted as an improvement. I would provide a reference to an external source which discusses the issue about the opening angle being close to but not exactly zero - but I don't know of one and I doubt that one exists. Chriskb19 (talk) 18:37, 19 April 2018 (UTC)
Please provide a source. If there is none, Wikipedia cannot accept it — per policy wp:VERIFIABILITY. - DVdm (talk) 18:43, 19 April 2018 (UTC)
Is that fair? Is there a source for the old image that this one replaced? And without taking a position on its correctness, Chriskb19 is correct that the new figure coincides with the math that is written in the pair production article. Waleswatcher (talk) 18:48, 19 April 2018 (UTC)
If you are not willing to take Chriskb19 at his word, then no picture would be better than a picture which is wrong. JRSpriggs (talk) 19:04, 19 April 2018 (UTC)
(edit conflict) As we know per wp:CIRCULAR, Wikipedia is not a good source. And all images found with [7] show large angles, even if the angles are indeed small very near to the place of creation (but getting larger due to the presence of a magnetic field). Anyway, if it is indeed true (which it probably is) and sufficiently important, then surely a source should be easy to find? Please note that I do like Chriskb19's picture. - DVdm (talk) 19:11, 19 April 2018 (UTC)
Well, a google image search for "pair production cloud chamber" comes up with a bunch of images. The angle is indeed quite small in most of those. Perhaps if one is in the public domain we could use it. Waleswatcher (talk) 19:15, 19 April 2018 (UTC)
As before, I do not quite understand what you want a source for. Do you want a source to substantiate the maths in Pair Production which shows that the angle is exactly zero given the approximations stated there? (That should be possible but it is not really my job as I am not introducing this.) Do you want a source to show it is not exactly zero when no approximation is used? (Harder to find as experts do not worry about this.) I believe you want a source with a picture/photo but a single picture does not prove anything. You would need tens of pictures, selected without bias, to substantiate that the claim is reasonable and it would not be a proof. (Incidentally you cannot use a Feynman diagram, as in that Google search, as each one is a space-time diagram and we need a space-space diagram to see an angle. Hence my contributed figure, which I have not found in any of the main textbooks.) But if a single photo would help - of a bubble chamber or a more recent electronic detector - then I am sure one can be found. Presumably one from me would not be appropriate if you don't trust my word as an expert. Chriskb19 (talk) 20:11, 19 April 2018 (UTC)
I don't see any Feynman diagrams when I do that search, just 10s of photos of cloud chamber events that support your claim. Maybe you need to take off the quote marks, and be sure you are doing an image search. Anyway I guess we have consensus now. Waleswatcher (talk) 09:22, 21 April 2018 (UTC)
An interesting essay to read is wp:EXPERT. - DVdm (talk) 20:26, 19 April 2018 (UTC)
In standard physics textbook exercices, the angle may not be negligible. In cloud chambers photos, the angle is small but noticeable. We could add the photo without the "θ close to zero", but then again, is the original wrong? We need sources to settle this argument. --MaoGo (talk) 20:33, 19 April 2018 (UTC)
I'm also taking a look at sources. For the moment I just found slide 66 of this [8] but I'm not sure if it is completely related. --MaoGo (talk) 20:53, 19 April 2018 (UTC)
Problem 1.48 page 77 from [9] estimates the angle to be on the order of mradians. NOTE: It is considered to be large enough to make additional measurements. --MaoGo (talk) 21:04, 19 April 2018 (UTC)

I think this picture [10] supports Chrisbk19's position, even if we cannot use it in the article. JRSpriggs (talk) 02:12, 20 April 2018 (UTC)

Ok, I think we can indeed use Chrisbk19's (nice looking) picture with its caption and this[1] source. I'll put it in place. Good find, MaoGo! - DVdm (talk) 08:11, 20 April 2018 (UTC)


  1. ^ Bianchini, Lorenzo (2017). Selected Exercises in Particle and Nuclear Physics. Springer. p. 79. ISBN 978-3-319-70494-4. Extract of page 79
  Done: [11], [12]. Feel free to hone. - DVdm (talk) 08:20, 20 April 2018 (UTC)
To Waleswatcher: Please do not confuse cloud chamber with bubble chamber. They are different devices. JRSpriggs (talk) 10:50, 21 April 2018 (UTC)

Can I boldly proceed with this ?

Discussion here. May I simply erase Laplace formula article and add a redirection? --MaoGo (talk) 10:22, 24 April 2018 (UTC)

That looks reasonable to me and no one has objected to the proposal. Go for it. --Mark viking (talk) 17:12, 24 April 2018 (UTC)
Done --MaoGo (talk) 11:14, 25 April 2018 (UTC)

Thermal energy to be converted to a disambiguation page

The recent deletion proposal ended without a consensus for deletion. However, a strong argument emerged for converting thermal energy to a DAB page. The argument is that "thermal energy" doesn't have a distinct well-defined meaning in thermodynamics. Rather, it can refer to heat, sensible heat, internal energy, or kT (energy), all of which have their own wiki article. Unless there are objections (I'll wait a few days) I intend to go ahead and do that, as I've already stated on Talk:Thermal_energy. Waleswatcher (talk) 10:46, 27 April 2018 (UTC)

Merging Entropy and Introduction to entropy

Over at the talk page for Entropy, User: made the following suggestion: "If we submit a merge request with introduction to entropy and break up section 6 then I think that's the best start. Then this article is responsible for both audiences so there's no cop out. 6.1 can join the definitions, a lot of 6.2 onwards can be merged down into 7 because "Applications" and "Approaches to Understanding" mostly mean similar things as presented here" (the section numbers refer to Entropy). I think merging the two is a good idea, both because Introduction to entropy is not very well written, and because it shouldn't be necessary at all. Instead, the entropy article itself should do a good job of explaining entropy, and if needed can have a non- or less-technical introduction section. Waleswatcher (talk) 21:11, 27 April 2018 (UTC)

A link to a DAB page

GNSS positioning calculation links to the DAB page Transit time. I'm not sure if either Radar#Transit time or Time of flight would be a good target, so expert attention in solving this problem would be appreciated. Thanks in advance, Narky Blert (talk) 14:53, 27 April 2018 (UTC)

I clarified what was meant. One could link to time of flight if one wanted, although hopefully it is now clear enough from context. --Mark viking (talk) 17:38, 27 April 2018 (UTC)
Thanks. I'm all in favour of simple in-line explanations over potentially confusing bluelinks. They're more helpful to readers. Narky Blert (talk) 09:16, 28 April 2018 (UTC)

Astronomy/astrophysics items being discussed at Talk:List of unsolved problems in physics

I've got an opinion, and other people surely do too. XOR'easter (talk) 14:23, 28 April 2018 (UTC)

Template:Scientists whose names are used as SI units

Template:Scientists whose names are used as SI units has been put up for deletion. SpinningSpark 16:14, 30 April 2018 (UTC)

Return to the project page "WikiProject Physics/Archive April 2018".