Wikipedia talk:WikiProject Physics/Archive December 2020

Polar form of the Dirac equation

I PROD'ed the above. The article contains an equation that, as currently written, is fundamentally wrong on multiple levels; a discussion with the original author on the talk page makes it clear that the original author is quite unaware of the mistakes, or how to fix them. As this is an arcane topic (how to correctly couple spinor fields to torsion in gravitation), it seems highly unlikely that anyone will show up and fix this (especially since the article is misnamed, these are not your father's polar coordinates) and so PROD'ing for deletion seems like the only reasonable choice. Besides, Wikipedia already has other articles that already explain how to correctly couple spinor fields to torsion, so having an article on a confusing equation that cannot be explained is ... just wrong. 67.198.37.16 (talk) 19:58, 22 November 2020 (UTC)

On Talk:Polar form of the Dirac equation, the original author of the page says that they're the author of 3 of the references, so we have a bit of a WP:COI issue. It's probably best just to let the page die. XOR'easter (talk) 20:05, 22 November 2020 (UTC)

For the record, it was deleted yesterday. XOR'easter (talk) 16:40, 1 December 2020 (UTC)

Whitehead's theory of gravitation (again)

Anyone curious about obsolete theories of gravity? A while back, I took a look at the Whitehead's theory of gravitation article and put some effort into the prose and the referencing. As I recall, I thought about adding more details about the formulae, but then had a moment of "there's no good notation for this!" and tossed my hands in the air, figuratively speaking. Prompted by John Baez on the Talk page, I took another stab at it, but I'm sure it can still be improved upon. XOR'easter (talk) 16:39, 1 December 2020 (UTC)

I find the notation hard to understand, but that's pretty common in Wikipedia articles so I'd say this is a big step forwards. Someday maybe I'll take a crack at understanding Whitehead's theory better and then I'll reread this and try to polish it up. Maybe someone else will beat me to it! John Baez (talk) 18:30, 6 December 2020 (UTC)

Anyone interested in an ELKO study group?

(edited since first post)

In the wake of the the Mass dimension one fermions AfD, I thought that it might be worthwhile to figure out what the heck this ELKO thing is. I think I've found an answer; its an 8-component spinor (see below). A key issue is that the majority of the literature on it is incredibly disappointing, and is not written in a fashion that I find clear and coherent (see, however, exception below). Here's what I've been able to deduce so far:

• There are 30 or 40 distinct authors who have published maybe 50 or 80 papers on ELKO and/or MDOF, so this seems to have triggered popular interest.
• The primary, key source for this, Ahluwalia's monograph, that would hopefully "explain it all", has been written in a very mathematically naive fashion. This makes it hard to read, (for me) because the naivete makes many statements seem to be dubious, requiring double-checking. It's a wtf text that sheds almost no light at all on the topic, (its "dark" haha pun) and was a torture to read.
• Ah Hah!! Ta dah!! Found the answer!! Thanks to J. A. Nieto (who has a long track record of writing in a clear and easy-to-understand fashion): The ELKO spinor is a pair of Dirac spinors coupled with a twist (in the classical meaning of a "twist" in mathematics: a pair of things joined by an antisymmetric tensor, e.g. a torus with a twist is a klien bottle.). It solves this twisted Dirac eqn:

$\left(\gamma _{ab}^{\mu }\partial _{\mu }\delta _{A}^{B}-m\delta _{ab}{\varepsilon _{A}}^{B}\right)\psi _{B}^{b}=0$

where $a,b=0,3$ are the conventional Dirac spinor indexes, and $A,B=1,2$ where $\varepsilon ^{12}=1=-\varepsilon ^{21}$ is the totally antisymmetric tensor. This appears on page one of https://arxiv.org/pdf/1907.00740.pdf -- This is the first coherent and comprehensible thing I've found after bucket-loads of searching over the last 2-4 days.

I was deeply unhappy with the poor quality of the literature, until I found the eqn above. I'm planning to start a draft stub at Draft:ELKO Theory real soon now, which perhaps might be promotable to article space. Again, an invite to anyone who might want to explore more deeply. 67.198.37.16 (talk) 20:07, 23 November 2020 (UTC)

I'm "finished" with the draft, with no further plans for it, at the moment. Now that I understand what it is, it seems to actually be a really rather very dramatic (important) discovery of pretty much fundamental importance to the Standard Model. Yes, I know that sounds way over the top, but hey, I guess I'm easily excited. Take a look; if it makes sense, please consider moving to article space. 67.198.37.16 (talk) 22:20, 23 November 2020 (UTC)

It needs more references. Also double-check how ELKO is capitalized, as at least one of the two current sources uses Elko. –LaundryPizza03 (dc̄) 23:21, 23 November 2020 (UTC)

Heh. Maybe I'm not finished after all. I'm currently trying to get all of the signs correct for charge conjugation across several articles: Dirac matrices, Majorana spinor, bispinor, C-symmetry, Weyl spinor etc. etc., which should then hopefully result in a consistent discussion of charge conjugation across all articles. The next cool thing is that one can also have twisted bosons, not just fermions; you can build a whole duality of twists, "just like" the Hodge star but acting in the twisted space. It's really wild. But first things first: charge conjugation.... and yes, Elko is often lower-case; the original use was as an acronym, upper-case. About upper/lower case, I don't care. I'll add explanation. Yes, I will also add a few more references, after I read them. I want to avoid random low-quality references. 67.198.37.16 (talk) 07:15, 24 November 2020 (UTC)

Status update: Since ELKO claims to be a new relativistic wave equation that has been overlooked for almost 100 years, and since I find such a claim hard to believe, I'm trying very hard to make sure it is not due to some sign error. So I am very carefully checking everything. Since ELKO is an eigenstate of charge conjugation, I started by expanding charge conjugation, making sure it is 100% textbook compatible, and verifying all signs and equations. Next, I added charge conjugation to gamma matrices and to Dirac equation again verifying all signs and equations. Then, to verify Lorentz covariance, I had to update Lorentz group. Yesterday, I added the Lorentz covariance section to Weyl equation, carefully checking all signs against all the other articles, so that they are all consistent. This week, I hope to finish edits to Majorana equation, which, if all goes well, should finally make it clear exactly what ELKO is ... or isn't... with all equations, signs and definitions fully compatible across this entire range of articles (and compatible with all textbooks and articles I have access to.) So far, I have only checked the classical theory, the classical solutions. The quantum operators have additional minus signs and complex conjugates and etc. floating around, so that will need a second pass to get all definitions fully consistent. I thought I could get this done in days, but it has taken weeks. Again, anyone with the patience for this kind of detailed work is invited to participate. (I want to emphasize that this is potentially maybe very important. So, the Atiyah-Singer index theorem is almost 60 years old, and ELKO is saying "hey guys, you missed one of the two cases". Nambu got a Nobel prize for chiral symmetry breaking in 2008, and ELKO is saying "oh hey, by the way, you missed one of the two cases". Now maybe it's nothing, maybe it all evaporates before it gets up into those higher echelons, but still, I find it gobsmacking to contemplate.) (Nambu taught me QFT when I was but a young lad...) 67.198.37.16 (talk) 19:11, 7 December 2020 (UTC)

quarks and gluons in diagrams

• 
  Proton
• 
  Neutron
• 
  Antiproton
• 
  Antineutron

• 
  Proton 'flux tubes'
• 
  Neutron 'flux tubes'

There is a discussion in talk:proton about quark/gluon diagrams for the proton (and I presume others). The discussion suggests consensus here for any changes, though I don't see any discussion here. The discussion in Talk:Proton/Archive_1#diagram_of_quarks_in_proton seems to be a few years old. One question might be, how accurate should the diagram be? This one seems to allow quark-gluon, three-way gluon interaction, and four-way gluon interaction. Should the diagram show those? My original thought was to include both wavy-lines between quarks, and the wye diagram currently there in one diagram. (That is the combination of the two.) I don't think we have room for the infinite number of allowed diagrams. The current one seems to suggest only the three-way interaction. Gah4 (talk) 00:47, 6 November 2020 (UTC)

The diagram is accurate with respect to what it wants to depict. Namely, there are interactions between quarks and gluons. It is not a depiction of gluon flux tubes (which is the overall contribution of all possible interactions), and I would oppose showing such an advanced sub-topic in a diagram that's made to be understood for all levels, from high school to grad school. Headbomb {t · c · p · b} 00:54, 6 November 2020 (UTC)

Which diagram do you prefer? Since they don't have names yet, the delta or wye diagram. (The names used in three-phase power.) Gah4 (talk) 01:02, 6 November 2020 (UTC)

The one we currently have. I won't know what 'wye' means. Headbomb {t · c · p · b} 01:03, 6 November 2020 (UTC)

Let's ping others from the Quark FA for their input, @TimothyRias, Casliber, RJHall, Anonymous Dissident, A. di M., Cryptic C62, and Jimfbleak: Headbomb {t · c · p · b} 01:15, 6 November 2020 (UTC)

As a particle physicist: I don't care, it's illustrating "quarks interact via gluons" in both cases. I think I have said that in a previous discussion already. I think the delta diagram has a nicer style of the gluon lines. @Headbomb: Y-Δ transform#Demonstration --mfb (talk) 17:25, 6 November 2020 (UTC)

I think the diagram we currently have is fine. Headbomb makes a good point that this illustration is intended for a wide audience. XOR'easter (talk) 19:08, 6 November 2020 (UTC)

The wye diagrams are slightly more correct, in that a quark never emits two gluons "at the same time" (as shown in the delta diagrams) The wye diagrams are correct, not only in this, but also in that they show that three gluons can interact with one-another, which is one of the key ideas behind non-abelian gauge theories. Just don't call them "flux tubes", just say that they show the ordinary gluon-gluon interaction. 67.198.37.16 (talk) 05:48, 11 November 2020 (UTC)

They don't emit and absorb at the same time, depending on your time resolution. How much time difference does there need to be between two emissions? Gah4 (talk) 00:41, 16 November 2020 (UTC)

If we use such diagrams in any context where they would suggest the readers different things, we're doing it wrong anyway, as they're supposed to be just a generic illustration. Anyway, I like Gah4's suggestion of showing both the Y and the Δ. — A. di M.  22:53, 15 November 2020 (UTC)

If we go with the Y, then we will need to create Y diagrams for the antiproton and antineutron. I don't know what will happen if we choose to show both the Y and the Δ diagrams. –LaundryPizza03 (dc̄) 02:25, 16 November 2020 (UTC)

To clarify, I mean the Y and Δ superimposed in the same figure, kinda like this. — A. di M.  10:09, 16 November 2020 (UTC)

see: c:Commons:GL/I#Representation_of_the_gluon_field_in_the_nucleons --Mrmw (talk) 11:56, 16 November 2020 (UTC)

• 
• 
• 
• 
• 
• 
• c:File:Quark structure antiproton.svg
• 

Sorry for the late reply, I just now saw User:Gah4 and User:A. di M. and User:LaundryPizza03 comments above. By "at the same time", what I mean is that the Lagrangian for quarks has the generic form ${\overline {\psi }}(\partial +A)\psi$ where psi is the quark field, and the A is the gluon field. The way this is to be read (if it is converted into a scattering amplitude, or an s-matrix) is that a quark comes in (the psi-bar) and either propagates ("wiggles around in a differential equation like way") (the partial symbol) or it hits (emits/absorbs) one and exactly one gluon (the A) and then it leaves (the psi). That's it -- comes in, hits one gluon, leaves. The Lagrangian for gluons has the generic form $(\partial A+[A,A])^{2}$ which can be read as saying "gluons propagate" (the partial-A part - one gluon comes in one goes out) or three gluons interact or four gluons interact (the products involving the [A,A] term.) The electromagnetic field does not have the [A,A] term, and so photons can only propagate. This three-gluon interaction is what makes gluons so unique and distinct (and is the reason for all the hoopla about Yang-Mills).

So here's the deal with the Delta diagram: with a suitable relablelling, and a suitable "time scale", it would also be an accurate diagram for Helium - one nucleus, two electrons, and some photons bouncing between the nucleus and the electrons, keeping the whole thing in a stable, bound state. The Wye diagram could never-ever describe Helium, because three photons just cannot interact in that Wye kind of way. The Wye is very unique to QCD.

For the "at the same time", for a helium atom, you could draw a diagram with 3 particles (nucleus, the two electrons) and 42 different photons going every which-way, but the photons must be two-ended: must always begin and end on the nucleus/electron. For QCD, you could draw a diagram with 3 quarks and 42 gluons, but now the gluons can bump into each other, so they form a big random network of wiggly lines. So, when you add time, this is how these diagrams differ. Anyway, that is why I like the Wye. The Delta for quarks isn't "wrong", its just maybe (mildly?) misleading, while the Wye diagram kills two birds with one stone... 67.198.37.16 (talk) 04:20, 23 November 2020 (UTC)

To me, the problem with wye is that it seems to suggest that the only interaction is the three-way version. Or, using your analogy, that there are always two birds, or maybe that birds always die in pairs. OK, another possibility is like the wye diagram, but with a big squiggly blob in the center. That is, gluons go into the blob, strange (oops) things happen, and gluons come out. But I think, as someone else said, the diagram doesn't have to be too accurate. All it needs to say is that there are three quarks, and that there are interactions between them. People who understand it in more detail will do without the need for a visual reminder. OK, we could put in the Feynman diagrams for the more detailed interactions, which are less visual but more accurate. Gah4 (talk) 06:31, 23 November 2020 (UTC)

• The wye-style diagram is superior by far; the delta diagram has misinformed untold millions of casual learners of elementary physics. Please remember: the diagram we choose here has a large impact not only on readers here, but on more derived educational materials, such as popular science videos on YouTube. Such producers rely on the material we present here, and so, our misinformation here ends up spreading across the globe. It is unacceptable, and the delta-apologists are to blame.

To me, leaving the inaccurate delta diagram is as irresponsible as only showing the Kekulé diagram for Benzene. The Kekulé diagram misleads learners into thinking that there are permanent double bonds in the benzene ring, or that they actually alternate between each other. Consequently, for aromatic species and other cases of delocalization, the policy has been to avoid misleading the public and represent the delocalization with dashed lines, especially for simple inorganic species which have an especial pedagogical importance. Look at Nitrogen dioxide or Carbonate or Ozone or any of those.

The wye-style diagram depicts what the gluons are actually doing in much the same way that the dotted lines do for delocalized electrons. The delta-style diagram is as misleading and unhelpful as a showing a single resonance structure for carboxylate anion, or nitrogen dioxide or ozone, or what have you. BirdValiant (talk) 20:41, 9 December 2020 (UTC)

the delta diagram has misinformed untold millions of casual learners of elementary physics The diagram shows something very simple, there are interactions between quarks and gluons. That's it. Gluon flux tubes (which is the net result of the contributions of all gluon interactions and cannot be summarized as single three-vertex gluon interaction) is something only seen at the PhD level and beyond. This is no worse than the 'misinformation' of showing only three valence quarks, or the misinformation depicting the red/green/blue colour charge as the colours red green and blue. We don't need to show sea quarks, gluon-gluon interactions, high-order feynman diagram contributions, and all that other stuff in what is meant to be a quick visual aid. The Y-diagram is not as accessible, is more convoluted, and equally if not more wrong than the normal diagram. This is the equivalent of a Bohr diagram of the atom. No, electrons don't orbit the nucleus like planets, but it's still convenient in summarizing the basic fact that there's a electrons orbiting a nucleus. File:7 nitrogen (N) Bohr model.png is a still good diagram for Nitrogen, even if the electronic cloud is nowhere near that shape. Headbomb {t · c · p · b} 20:55, 9 December 2020 (UTC)

Supersymmetry as a quantum group

I prodded this as unreferenced. It has sat without cites since 2007 and the title does not seem to appear anywhere outside of Wikipedia. It might be good content or it might be original research. I don't have the expertise to tell. - SimonP (talk) 21:03, 9 December 2020 (UTC)

Another COI editor

An editor, Luca-Spinor-Torsion, whose real name is Luca Fabbri, has added citations to his own papers in Dirac equation and De Broglie–Bohm theory. I've undone the edits. Tercer (talk) 13:44, 10 December 2020 (UTC)

I re-removed those citations [1][2] as they'd been re-inserted without explanation. XOR'easter (talk) 17:27, 10 December 2020 (UTC)

Big Freeze

Big Freeze is currently up for discussion at RfD. I thought you might be interested.

Also, looking at wikt:en:Big Freeze#English, the definition on Wiktionary needs a rewrite. Anyone want to give it a try?

-- 67.70.26.89 (talk) 11:02, 12 December 2020 (UTC)

Sudbury Neutrino Observatory - HEP INSPIRE search

https://en.wikipedia.org/wiki/Sudbury_Neutrino_Observatory has a dead link that would be an easy fix for someone who knows what they are talking about. The database for the original link HEP Spires was migrated to HEP Inspire. I left a note on the talk page but that might not be found this century, so I thought I'd put it somewhere in the Physics department. Hope someone can do the fix. Sorry if this was the wrong place to ask. Thanks. — Preceding unsigned comment added by ‎2600:1700:1c60:45e0:a9a6:aa4d:32ae:1bc4 (talk • contribs)

Fixed; thanks for calling it to our attention. XOR'easter (talk) 02:36, 16 December 2020 (UTC)

Heaviside-Feynman formula

Taking a guess, I accepted this to keep it from being deleted at 6 months. It would seem related to Jefimenko's equations, but I'm not at all an expert. I cannot tell if a merge is appropriate, or whatever, I leave it to the physics people here. DGG ( talk ) 00:09, 15 December 2020 (UTC)

User:DGG these two articles are about almost the same things so they can be in one longer article or they can be separate. Both are fine.

The main difference is that the Heaviside-Feynman formula is only for a point charge but the Jefimenko equations can apply to a point or a more general charge distribution. The textbook Classical Electrodynamics (book) talks about both and derives Heaviside-Feynman formula from Jefimenko's equations. They describe the same phenomenon and sometimes the naming is confusing. For example, "The electromagnetic waves in retarded regime for time dependent current distributions are entirely described by the generalized Jefimenko equations (also called Heaviside-Feynman formula)." in [3]. < Atom (Anomalies) 22:24, 21 December 2020 (UTC)

so the H-F is essentially a special case, which is what I thought. If they can be easily confused, they'll do better as one article with a redirect----perhaps you can merge them. DGG ( talk ) 00:25, 22 December 2020 (UTC)

I've merged Heaviside-Feynman formula into Jefimenko's equations. XOR'easter (talk) 00:38, 22 December 2020 (UTC)

Wave function collapse and QFT

Additional voices might be helpful over here:

• Wave function collapse (edit | talk | history | links | watch | logs)

Cheers, XOR'easter (talk) 18:11, 11 December 2020 (UTC)

That was interesting. Thank you. 67.198.37.16 (talk) 04:42, 23 December 2020 (UTC)

draft article about "fragments of energy" theory

For the past week, an paper has been circulating about a theory that fragments of Energy are the fundamental building blocks of the universe. At what point does a new idea merit a wikipedia page? I don't have a horse in the race, but I found the theory interesting so I started one that collected the basic information proposed in the theory. Clearly someone with more knowledge on particle physics than myself should probably be involved in drafting the article. Anyone interested in looking it over, giving constructive criticism, contributing?frey (talk) 18:17, 15 December 2020 (UTC)

At the risk of sounding harsh, revolutionary new ideas about physics are a dime a dozen. Moreover, it's easy for them to generate spurious media coverage, thanks to websites churning press releases for clicks. The sources in the draft are all either that or by the inventors themselves. So far, this is a long way from meeting our noteworthiness standards even for marginal science. XOR'easter (talk) 18:58, 15 December 2020 (UTC)

I took at look at the article. Don't waste your time, it's complete nonsense. Tercer (talk) 20:07, 15 December 2020 (UTC)

Piling on. When I saw the headline, I scratched my head - isn't that what Planck's blackbody and Einsteins photoelectric effect showed? That its all "fragments of energy"? I once studied how GPS works, and found myself reading a published article, in some engineering journal, that disproved special relativity. How, you may wonder? Why, its easy! GPS provides a universal time coordinate, everywhere! It took 8 pages to say that; the argumentation was quite clever and craftily constructed. Anyway, I know that this comment is off-topic and inappropriate for WP discussion, but I just thought I'd provide some light entertainment for the readers of this page. 67.198.37.16 (talk) 05:20, 23 December 2020 (UTC)

FAR notice

I have nominated Astrophysics Data System for a featured article review here. Please join the discussion on whether this article meets featured article criteria. Articles are typically reviewed for two weeks. If substantial concerns are not addressed during the review period, the article will be moved to the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Delist" the article's featured status. The instructions for the review process are here. Hog Farm _Bacon 05:43, 23 December 2020 (UTC)

Carchasm depopulating "Concepts in Physics"

@Carchasm: Carchasm (talk · contribs) has been depopulating Category:Concepts in physics, removing many important articles from that category. Is this appropriate? JRSpriggs (talk) 17:03, 22 December 2020 (UTC)

I have been wondering about this too —see User talk:Carchasm#Careful— but I didn't feel like trying to stop a runaway train... - DVdm (talk) 17:14, 22 December 2020 (UTC)

I also saw that. I did notice that the page of the category itself asks for it to be depopulated, so I guess it's fine. Ultimately I don't really care one way or the other. Tercer (talk) 17:31, 22 December 2020 (UTC)

The request is to re-categorise to sub-topics "where applicable" and certainly not to remove completely. Some of the sub-topic categorisation has been inappropriate and some has been undone already. Feel free to pile in if you see one that doesn't make sense. Lithopsian (talk) 17:40, 22 December 2020 (UTC)

Sorting articles more specifically seems a useful thing to do, overall. I did revert a couple [4][5]. XOR'easter (talk) 18:19, 22 December 2020 (UTC)

The category had gotten turned into a dumping ground for all matter of pages (fields of research, equations, quantities, introductions, history articles - basically anything that wasn't a person or organization). I think it's probably a good long-term goal to completely empty it if we can find/create better categories as per WP:OCMISC, but I had started moving things to (admittedly, subjectively) "better" categories for the time being. For example, coherence can certainly be a quantity if we're talking about measuring the amount of coherence between two waves, but it does seem like it should both be in Category:Physical quantities and some other category that maybe doesn't exist yet, as well as any optics specific categories (properties of light, maybe?). If people feel strongly that a certain page should remain in Category:Concepts in physics for now though I'm not going to push back on that... Though in the interest of openness I'm also the one who added the Category diffusion template and the one who moved the Quantities, Equations, and Phenomena Categories to be subcategories of Category:Concepts in physics rather than Category:Physics so if that's not the direction people think we should go I'm open to discussing that. - car chasm (talk) 18:56, 22 December 2020 (UTC)

I always thought the category was for concepts used in physics: Like Internal energy or mass-energy equivalence - they might relate to physical quantities, but they are also concepts you learn about while studying physics. Though I note it is hard to define any criteria for inclusion for that, so maybe it is better to find more selective categories. Footlessmouse (talk) 19:15, 22 December 2020 (UTC)

"Concepts" categories tend to become a dumping ground for things people haven't bothered to properly categorize. They do need to be cleaned up every now and then, moving articles to more appropriate categories.--Srleffler (talk) 08:19, 23 December 2020 (UTC)

Quantum Cellular Automata

I would like to open up a discussion here on the "Langtons Ant Wave Equation", a derivation using the Telegraphers equation along with a circuit diagram and Octave script could be a starting point for our discussion, it would be great to have wikipedia responsible for increasing the IQ level of planet Earth. — Preceding unsigned comment added by Dakoder (talk • contribs) 11:01, 28 December 2020 (UTC)