Wikipedia talk:WikiProject Physics/Archive January 2014

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The reorganization of Category:Flight is being discussed at Talk:Aviation -- (talk) 01:24, 1 January 2014 (UTC)

New article on "Geometric Mechanics"

Please see the new article Geometric Mechanics. I have never heard of this subject before, have you? Either the article should be substantially improved or removed. JRSpriggs (talk) 06:52, 31 December 2013 (UTC)

Could be notable as there is literature on the subject with the title "Geometric mechanics", e.g. first page of google books [1] by Darryl D. Holm (2008), Richard Talman (2008), James Montaldi, ‎Tudor Ratiu (2005), Ovidiu Calin, ‎Der-Chen Chang (2006), Darryl D. Holm, ‎Tanya Schmah, ‎Cristina Stoica (2009), Jared M. Maruskin (2012), etc... (some authors are already in the article), and some pdfs [2], [3], [4] (for external links). But as you say it needs a lot more clarification and rewriting. M∧Ŝc2ħεИτlk 10:38, 31 December 2013 (UTC)
From what I have heard of geometric mechanics (which agrees pretty much with what is in the article), it is certainly notable enough for an article here. As always, the first stab at an article is not perfect (in particular, it is rather advanced), but I think it is not bad. -- Jitse Niesen (talk) 15:10, 31 December 2013 (UTC)
While there have always been treatments of mechanics from the geometric point of view. this is a real subfield of mathematical classical mechanics emphasizing symmetry and reductions. Geometric Mechanics, Lagrangian Reduction, and Nonholonomic Systems is a good survey of the field from the turn of the century and Maschen has pointed out more modern sources. The article should e renamed Geometric mechanics. --Mark viking (talk) 17:50, 31 December 2013 (UTC)
I renamed it to Geometric mechanics. M∧Ŝc2ħεИτlk 10:10, 1 January 2014 (UTC)

Rodin coil

Rodin Coil has been prodded by an IP. I found a few (weaker) sources at Does anyone know anything about this? WhatamIdoing (talk) 23:18, 3 January 2014 (UTC)

No significant sources. Looks like crank (person) stuff to me. Xxanthippe (talk) 23:47, 3 January 2014 (UTC).
"Rodin" has appeared here also. Possibly a crank. The reliability of the only source in the article looks dubious too.M∧Ŝc2ħεИτlk 00:00, 4 January 2014 (UTC)
The reliability of that source is zero. It's just a blog. Anyway, we need hundreds of sources for an article. Xxanthippe (talk) 01:27, 4 January 2014 (UTC).

Unification theory: just needs a sysop

When I wrote the history of subatomic physics article I discovered that Unification theory (edit | talk | history | links | watch | logs) redirects to Grand Unified Theory and, moreover, some “provident” Wikipedian protected the redirect indefinitely! The reasonable target would be “unified field theory” of course; note “unified theory” redirects there. It is a concept, a generic term. For example, the Kaluza–Klein theory is a “unification theory”, but not a GUT. BTW the “unified field theory” article IMHO strays into the topic of GUT, but it is a problem of secondary importance. Incnis Mrsi (talk) 23:41, 5 January 2014 (UTC)

After a very short glance there seems to be another contender for that term; compare for example these papers. Most Google Scholar hits for "unification theory" seemed to refer not to physics but to automated reasoning and AI research. Those that were about physics almost exclusively talked of a Grand Unification Theory (to which this once redirected), so the current redirect seems to have some merit. Huon (talk) 00:07, 6 January 2014 (UTC)
(edit conflict)Nice new article (history of subatomic physics), good work! Sorry not to be of help (as usual), since I'm not an admin...
Yes, nice start. It's harder than it might seem to write general survey stuff. Incidentally, there are are a few theorists who claim that quarks and leptons are composite particles, but this is as yet far from mainstream and has no experimental support. Xxanthippe (talk) 01:20, 6 January 2014 (UTC).
I also agree that unified field theories are not equivalent to GUTs, since GUTs = strong + weak + EM. M∧Ŝc2ħεИτlk 00:11, 6 January 2014 (UTC)
Yes, even classical EM is a unified theory. YohanN7 (talk) 00:26, 6 January 2014 (UTC)

AFC and Convection–diffusion equation

User:Tikuko raised an AFC here at WP mathematics. Opinions may help when possible. M∧Ŝc2ħεИτlk 11:20, 28 December 2013 (UTC)

Decent article, misleading title. I have proposed renaming it to "Numerical solution of the convection–diffusion equation". Please discuss at Talk:Transient convection diffusion equation. --Steve (talk) 05:34, 6 January 2014 (UTC)

High energy nuclear physics and Relativistic nuclear collisions

There are fairly short separate articles on high energy nuclear physics and relativistic nuclear collisions. They seem to cover much the same area, though both seem a bit patchy. It's not my field, so I don't want to just pile in and suggest merging them so I thought I'd raise it here first - are these really different topics or just different aspects of the same one, and would it be useful to merge the two articles, or reorganise them somehow to cover them separately? Djr32 (talk) 22:56, 1 January 2014 (UTC)

"High-energy" usually refers to "high energies and speeds" where relativistic physics is required, as a rule of thumb. Actually, more often "high-energy physics" refers to the physics of subatomic particles in high-energy collisions.These could probably be merged, very much overlapping each other. M∧Ŝc2ħεИτlk 00:00, 4 January 2014 (UTC)
One could not really tell from these relatively undeveloped articles, but the two topics are a bit different. High energy nuclear physics is a subfield of nuclear physics concerning behavior in the high energy regime. It encompasses both theory and experiment. Relativistic nuclear collisions is an experimental technique used to study nuclear systems in the high energy regime. It is analogous to the relation between the field of high energy particle physics and the technique of using relativistic particle collisions to study the field. That said, pragmatically the articles are just unreferenced start/stubs at this point and I agree with Maschen that merging them seems reasonable, with no prejudice to splitting them apart again when someone wants to develop them more thoroughly. --Mark viking (talk) 01:04, 4 January 2014 (UTC)
Fair points, but there is still overlap in that they both include experimental study. I don't have objections either way (merging or splitting at any time), but a merge seems to make more sense. As usual it comes down to what the most reliable sources say. M∧Ŝc2ħεИτlk 01:28, 4 January 2014 (UTC)
Thanks both for the replies. I agree with your point that one is a technique while the other is a field of study that uses it. The current high energy nuclear physics article is entirely about heavy ion collisions, but that's more about the current article being incomplete rather than about what high energy nuclear physics covers. Having said that, I'm not sure that the term "High Energy Nuclear Physics" is very widely used - RHIC and ALICE both describe themselves in terms of investigating quark-gluon plasma rather than saying they're doing nuclear physics or high-energy physics. (I guess that's always the way - in reality there are no hard boundaries between different areas of knowledge.) As Mark said, the pragmatic approach given what we have now is probably to merge them (to which title?) with the possibility of separating them later. I'll put some merge proposal tags on over the weekend to see if anyone objects. Djr32 (talk) 16:49, 4 January 2014 (UTC)
Maybe just merge Relativistic nuclear collisions into High energy nuclear physics, without changing the title of the latter? Or for a merged title how about "Relativistic nuclear physics" (is this too broad)? M∧Ŝc2ħεИτlk 17:10, 4 January 2014 (UTC)
I think "relativistic nuclear physics" would be misleading - the interesting physics happens because the ions whack into each other really hard, it's just that you need to start off with them at relativistic speeds in order to get them to do that. In fact everything that matters happens when the nuclei are nearly stationary. Merging to "high energy nuclear physics" would seem fine to me. Djr32 (talk) 19:45, 4 January 2014 (UTC)

Let's wait a few weeks, then merge as we've said. M∧Ŝc2ħεИτlk 20:30, 6 January 2014 (UTC)

AfC submission

Care having a look a this submission? Thanks, FoCuSandLeArN (talk) 22:14, 7 January 2014 (UTC)

After a five second glance it look OK to me. Xxanthippe (talk) 22:37, 7 January 2014 (UTC).
The permission information on the images is inadequate. Stigmatella aurantiaca (talk) 01:36, 8 January 2014 (UTC)
It's excellent to see that someone is writing an article on the separated oscillatory fields method. At a glance, the text of the article looks good. The only immediate issue I can see is that the images need to have their permissions clarified. Zueignung (talk) 18:47, 8 January 2014 (UTC)

Wikipedia talk:Articles for creation/Estakhr constant (physics)

Dear physics experts: The above old abandoned Afc submission will soon be deleted as a stale draft. Is this a notable topic, and are there reliable sources to support it? —Anne Delong (talk) 17:51, 8 January 2014 (UTC)

I'm sure this has been proposed at least once or twice before. Just delete it. It looks like POV pushing. M∧Ŝc2ħεИτlk 18:14, 8 January 2014 (UTC)
This is a fringe topic and there don't seem to be sources that make it notable fringe. Best for it to be deleted. --Mark viking (talk) 19:17, 8 January 2014 (UTC)
Thanks; I have nominated it for deletion. Only (17,000 more to go...) I asked at Wikiproject Geology about this submission: Wikipedia talk:Articles for creation/Infrasonic passive differential spectroscopy (IPDS), but haven't received a response. Maybe it's more of a physics topic? —Anne Delong (talk) 19:59, 8 January 2014 (UTC)
It is a physical geology topic, but I guess there wasn't interest or available editors. My unexpert opinion is that IPDS is a real technique, but it is a proprietary version of the more general technique called Passive seismic. There are 16 hits for it in GScholar, not a lot. Given that the article is somewhat promotional and the dearth of independent RS, this topic may not be notable. --Mark viking (talk) 21:16, 8 January 2014 (UTC)
Thanks, Mark. I'll let it go. —Anne Delong (talk) 03:05, 9 January 2014 (UTC)

"Draft" rating

I suggest that this wikiproject implement the new "Draft"-class and categorize into Category: Draft-Class physics articles‎, for pages in the WP:Drafts namespace that was recently initiated. This would allow tracking of articles related to this wikiproject that are in draft form, which members of this wikiproject may wish to improve and move into the mainspace. -- (talk) 07:09, 9 January 2014 (UTC)

When AfC switches over to DRAFT, then those AfC submissions can be tagged with this system, if the wikiproject upgrades its banner -- (talk) 04:17, 10 January 2014 (UTC)


FYI, aeronautics has been proposed to be renamed to aeronautical science, see talk:aeronautics -- (talk) 05:05, 10 January 2014 (UTC)

Merge Probability amplitude into Wavefunction

The probability amplitude article covers the same material as the wavefunction article, with some extra bits on diffraction and probability current which could be in the wavefunction article. The terms are synonymous, although "wavefunction" seems more widely used. Does anyone object to merging?

This has been proposed before in 2008 here. M∧Ŝc2ħεИτlk 20:23, 6 January 2014 (UTC)

The objection seems to be for probability amplitudes including spin, which is hardly a reason for not merging since wavefunctions can have spin. M∧Ŝc2ħεИτlk 20:30, 6 January 2014 (UTC)

Recall our long discussion about this. Probability amplitudes and wavefunctions aren't conceptually necessarily the same thing. (I haven't read the articles, and a merge might be in order anyway.) YohanN7 (talk) 20:37, 6 January 2014 (UTC)
The topics are thoroughly overlapping and could be explained together. Why have two articles describing things like continuity, normalization etc. instead of one? M∧Ŝc2ħεИτlk 20:41, 6 January 2014 (UTC)
Probability amplitude can probably be merged into Wavefunction forming a section there. The more general notion is wavefunction as a solution to a wave equation, spin or no spin, relativistic or not, while probability amplitude is an interpretation (one of several possible) that applies to nonrelativistic quantum mechanics only. YohanN7 (talk) 20:49, 6 January 2014 (UTC)
Yes, it may help to break the wavefunction article into sections starting with non-relativistic quantum mechanics with probability interpretations, the probability current and diffraction, etc. The terms are synonymously used in non-RQM (and not RQM). Then follow up by the wavefunction in RQM, including spin and spinors, etc. M∧Ŝc2ħεИτlk 21:01, 6 January 2014 (UTC)
Sounds like a good game-plan. Some wavefunctions (free particle solutions of RQM euqations) are used heavily in QFT too, especially in S-matrix calculations. YohanN7 (talk) 21:07, 6 January 2014 (UTC)
A merge looks OK, as long as the distinction between wave function and probability amplitude is maintained. A wave function is a mathematical object, originally used to calculate energy levels. A probability amplitude is the now common semantic interpretation of a wave function, at least in the non-relativistic case. That a wave function can be interpreted as a probability amplitude was a historically nontrivial and controversial hypothesis; Born got the Nobel prize in part for it. The wave function article itself claims that a wave function is a "complex number", confusing the issue with spin. --Mark viking (talk) 21:23, 6 January 2014 (UTC)
OMG what a crap is going on? These are just different things. Wave function is a particular implementation of the quantum state vector, that perfectly could be finite-dimensional (and thus its elements would not be functions on an infinite set). Probability amplitude is about another thing, more related to the Born rule than to waves or so. It is about the z ↦ | z |2 or zz z transform that allows to map complex L2 functions (do not matter either on some space with Lebesgue measure or on a discrete set) of the norm 1 to probability measures. Wave function is a piece of formalism. Amplitude is a piece of interpretation or possibly a translation (yes, a pun). Look at interwiki links on probability amplitude, at last. Incnis Mrsi (talk) 22:58, 6 January 2014 (UTC)
They are conceptually different things. No merge. Xxanthippe (talk) 23:05, 6 January 2014 (UTC).
One problem is that the respective articles (and much of the QM 101 literature) treat them as the same thing. A merge could clarify the situation and get the distinction right conceptually. They are distinct concepts indeed. One is an interpretation of the other. I don't mean that we should make it a tossed salad. Maintaining status quo doesn't seem good. Wavefunction is replete with references to the probability interpretation - and vice versa. YohanN7 (talk) 23:40, 6 January 2014 (UTC)
Why is it bad or wrong to explain two different things which can be confused within the same article? You want WP articles to be clearer, yet you also think it's clearer to have two entire articles which forces the reader to read both only to find overlapping similarities (superposition, normalization, ...)?
The sections Wave function of a free particle, normalizable states and Conservation of probabilities and the Continuity equation in Probability amplitude are entirely about non-relativistic "wavefunctions" where probability interpretations can be used. As YohanN7 says very well, a section in wavefunction which explains where, when, and why probability interpretations are possible would be beneficial... or not??
Relax, there will not be any merge for a few weeks anyway, unless there is overwhelming consensus not to merge.
And no, I don't think quantum state should be pulled into this, that is a separate and general article. M∧Ŝc2ħεИτlk 08:01, 7 January 2014 (UTC)

If merging makes too many people unhappy then probability amplitude should be completely rewritten to not look so similar to wavefunction (parts of wavefunction itself need rewriting). Readers will get confused between these articles as they stand (and as YohanN7 confirms). M∧Ŝc2ħεИτlk 08:07, 7 January 2014 (UTC)

When I was a maths student, I saw no difficulties in these things: yes, a Hilbert space; we know how their structure is simple. Yes, a measure; but we fortunately know the measure theory. Now I understand that these are, maybe, simple things in isolation, but it is not an easy thing to explain how z ↦ | z |2 defines the same transform of L2, both finite- and infinite-dimensional, for both atomic and non-atomic measures. To explain how these amplitudes are conceptually the same thing, although presentations differ. I started to rewrite it, but (except one off-topical and trivial section removed by me) I see surprisingly few things that IMHO have to be moved out of the article. BTW I apparently broke something about normalisation; possibly will fix it later. Can anybody help with the article further? Incnis Mrsi (talk) 10:59, 7 January 2014 (UTC)
@Incnis Mrsi: Thanks for all your edits on this. At some point maybe I'll edit the probability amplitude article, modern good references which spring to mind include QM (Zettili), QM (Schuam's), QM (Eisberg and Resnick), QM (Abers), slightly older are Feynman's volume 3 and Non-relativistic QM (Landau and Lifschitz), and Quanta: a handbook of concepts (Atkins), as and when I can get some of them in the library, and for an old reference Principles of QM (Dirac).
I'll scrap my proposal for merging since even if they were merged successfully, someone in the future would likely want to split them apart again anyway. The merge banners can be pulled down anytime.
Sorry to waste people's time on this... M∧Ŝc2ħεИτlk 17:56, 7 January 2014 (UTC)

No problems: the article required a reworking anyway. BTW, I found a problematical section that possibly should be expunged and moved to “wave function”: see talk: Probability amplitude #One-dimensional quantum tunnelling. Incnis Mrsi (talk) 12:16, 11 January 2014 (UTC)

Advice please: (Solid State) Fault Current Limiters and Superconducting Fault Current limiters

There are multiple issues with this article, it lacks balance and endorses one very new technology (high temperature superconductors) over the current mainstream technology (rectifiers or solid state). Others have also expressed objections to this article, and I am agreement with them - it lacks balance. See

1. It should be re-titled Superconducting Fault current limiters.

2. It wrongly dismisses non-superconductor devices as "properly termed fault current controllers." This is subjective, such terminology is not in use by major manufacturers, see item 3 below.

3. Non-superconducting FCLs are in regular commercial use. See$File/72007_pix_is_limiter_en_hires.pdf by the major manufacturer Schneider.

4. The links and references are titled falsely and overly optimistic. For ex, the references and links titled "YCBO-type FCL enters service....." and "First commercial FCL both have other titles.

5. This technology is not yet commercial mainstream and may have electrical or economic limitations, and yet it subjectively dismisses the mainstream alternative.

6. Recommend that this article be re-titled "Superconducting Fault current limiters." A new Wiki page is needed correctly titled "Fault current limiters" which discusses in a balanced manner the mainstream non-superconducting technology, and references "Superconducting Fault current limiters." ~~1capybara

7. Wikipedia (senior) editor Askedonty, commenting on the above, says "Note that the U.S. DOE prefer using the pair: HTS FCL vs. solid state FCL" here

8. Wikipedia (senior) editor Askedonty has suggested I ask WikiProject Physics for advice. I recommend a new Article on FCL which references both separate technologies. Or alternately, can I please recommend (and begin) a re-write of the existing FCL article in a more balanced manner?

9. Advice please! Thank you!1capybara (talk) 09:20, 7 January 2014 (UTC)

I'm forwarding your request to Wikipedia talk:WikiProject Engineering, Wikipedia talk:WikiProject Technology, Wikipedia talk:WikiProject Energy and Wikipedia talk:WikiProject Electronics. I agree that the subject deserves a better article and you may be right regarding a needed split between the genres. Regarding your point 5, Sfcl is entering mainstream, or at least it got some financing and support for it, see about the ECCOFLOW project for superc, and this page too. I suppose we will have to explain and document what are the mainstream alternatives. I suppose this will be about grids, and infrastructures. Where I'm concerned I'm very thankful but please do not grant me such recognition contradicted by my editcount or any of all the other numerable credits that I've been able to register. --Askedonty (talk) 16:42, 11 January 2014 (UTC)

AfC submission

Another one for you, about time. Regards, FoCuSandLeArN (talk) 19:54, 9 January 2014 (UTC)

And yet another one. Is anyone interested in browsing the AfC queue regularly? We get heaps of these. FoCuSandLeArN (talk) 20:19, 15 January 2014 (UTC)
The time correction seems like WP:OR. Not sure why the elasticity article is OR, there are at least some citations (some mainspace articles have almost no citations at all, when they could). If others agree, maybe it could be entered into mainspace and reworked by continuum mechanics experts?
About looking through the AFC queue, I'll try more often. Thank you for bringing the articles to the attention of the wikiprojects, it seems thankless but you shouldn't think that. M∧Ŝc2ħεИτlk 20:49, 15 January 2014 (UTC)
The time correction article Is OR and the refs are mostly sourced to one author. This looks like fringe to me. I left an afc comment in the continuum mechanics article. It's a close copy of a recent tech report, so looks like OR and synth (as well as COI).
I've done some browsing of the AfC queue (mostly the oldest in the queue) and brought a couple to mainspace. But drinking from that firehose nearly drowns me :) I admire your and Anne's stamina and appreciate the pointers you all give here. --Mark viking (talk) 21:02, 15 January 2014 (UTC)
I appreciate your appreciation! It is daunting work. I'll leave you another one for today Face-smile.svg. FoCuSandLeArN (talk) 00:01, 17 January 2014 (UTC)

Pinhole (optics)

See talk:Pinhole (optics) where a discussion is going on about the scope of the article and its name -- (talk) 05:23, 17 January 2014 (UTC)

“Featured” bollocks from Atom

I do not know how happened out of this article, but anybody who watches it (and its talk page) during the last year knows that the situation is awful. Apparently no person with a diploma seriously read the article, and there is virtually no actual discussion supported by experienced editors. During this time following statements were observed (note I didn’t investigate who was the author of either):

When an electron is bound to an atom, it has a potential energy that is inversely proportional to its distance from the nucleus. This is measured by the amount of energy needed to unbind the electron from the atom…

and some related semi-literate crap — removed by me in February 2013 (see talk:Atom #Changes in Atom #Energy levels for details). Fortunately, I know quantum mechanics enough.

An electron… is not included in calculating atomic mass of an atom.

recently removed by me together with an off-topical section that mostly duplicated a content (also present in a “featured” article for years).

Atomic radius… is a measure of the distance out to which the electron cloud extends from the nucleus.

still present — see talk:Atom #Deletion.

Note that I am not an expert in atomic physics. Volunteer? Incnis Mrsi (talk) 11:03, 18 January 2014 (UTC)

Update: It revealed that a first-level section ==Fundamental Particles== [sic], together with atomic mass revelations, was created rather recently by certain Mahusha (talk · contribs), who has a hot user_talk. The edit history shows that his/her activity was spotted by Headbomb (talk · contribs), but ensuing actions were insufficient. Incnis Mrsi (talk) 11:27, 18 January 2014 (UTC)

Invitation to User Study

Would you be interested in participating in a user study? We are a team at University of Washington studying methods for finding collaborators within a Wikipedia community. We are looking for volunteers to evaluate a new visualization tool. All you need to do is to prepare for your laptop/desktop, web camera, and speaker for video communication with Google Hangout. We will provide you with a Amazon gift card in appreciation of your time and participation. For more information about this study, please visit our wiki page ( If you would like to participate in our user study, please send me a message at Wkmaster (talk) 18:28, 20 January 2014 (UTC).

Unification of terminology about spin

Two or three different problems simultaneously about the terminology in particle physics, but they are related.

Total angular momentum

Not to anyone’s surprise Total angular momentum (edit | talk | history | links | watch | logs) redirects to total angular momentum quantum number. But one can be surprised by a high number of inbound links. Many links from various subatomic particles are produced by the well-known JPC symbol, either directly from the “J” letter or in an annotation. If I understand correctly, this “J” is nothing but the particle’s spin and has little to do with t.a.m. operators considered in many-particles systems. Can anybody explain why is the spin referred to as “total angular momentum” in particle physics? Is it related to the confusion from the next subthread? Incnis Mrsi (talk) 15:53, 21 January 2014 (UTC)

Some thoughts related to this bizarre “total angular momentum” term are presented there. Particle physicists may distinguish “different composite particles”, such as mesons, by their spin, that they derive from total angular momentum. Incnis Mrsi (talk) 17:43, 21 January 2014 (UTC)

Spin (physics): the scope

The article is awful from the beginning. I certainly couldn’t understand what is the spin from it (unless my prior knowledge).

In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei.

First of all, I remind that the first experiment that established properties of the spin, the Stern–Gerlach experiment, was made on silver atoms in the ground state. Does the article mention atoms in a definite quantum state? Does the article explain why the ground state while, for non-zero spin, it is degenerate due to the global rotational symmetry? Second, what means “composite particles (hadrons)”: is it an implicit declaration that all composite particles are hadrons? Definitely wrong. Maybe, it is a restrictive clause (those composite particles that are hadrons)? It makes some sense, although it requires explanations, namely, conventions that make
“different particles”, singlet oxygen and triplet oxygen marginally different (although substantially the same), and two spin states of, say, the 1H atom “the same atom”, although there is no difference, in principle, between all three cases. Also, the article doesn’t mention quasiparticles (such as phonons, electron holes, and Cooper pairs), but it is less critical.

As I expected, the talk page is cluttered with quibbles of secondary importance. Even if somebody asked similar questions in the past, it is hard to find now.

Suggestions? Incnis Mrsi (talk) 15:53, 21 January 2014 (UTC)

Just “spin” or “spin quantum number”?

Yesterday I commented about the difference between the spin (a quantity inherent to a particle) and a quantum number. Now I realized where did the confusion between them come from.

All elementary particles of a given kind have the same magnitude of spin angular momentum, which is indicated by assigning the particle a spin quantum number.

Open the spin quantum number article:

In atomic physics, the spin quantum number is a quantum number that parameterizes the intrinsic angular momentum (or spin angular momentum, or simply spin) of a given particle. The spin quantum number is the fourth of a set of quantum numbers (the principal quantum number, the azimuthal quantum number, the magnetic quantum number, and the spin quantum number), which describe the unique quantum state of an electron and is designated by the letter s.

Good. It is clear that this s.q.n. is not “assigned”, but “parameterizes”. Does any other s.q.n. exist in physics? Incnis Mrsi (talk) 15:53, 21 January 2014 (UTC)

Quantum particle

Astonishingly, Quantum particle (edit | talk | history | links | watch | logs) since 2006 is a redirect to self-energy with an obscure meaning. It should be a redirect to some section in particle explaining something like is now present in particle statistics #Quantum statistics, namely that “quantum particle” is a particle whose degrees of freedom are described as its quantum state. Opinions? Incnis Mrsi (talk) 10:28, 21 January 2014 (UTC)

Good catch. A useful redirect may be to to Quantum mechanics itself, which talks about the quantum nature of particles in the lead and throughout the article. For someone who wants to learn about quantum particles, understanding wave-particle duality may be the first concept to grasp. --Mark viking (talk) 21:15, 21 January 2014 (UTC)
My first impression (without having read the involved articles) is that "quantum particle" should be an article of its own, or, at the very least, a section in "particle". The same thing goes for "classical (point) particle". What a "quantum particle " is should probably be described in terms of Lorentz transformation properties of the state vector of the particle. YohanN7 (talk) 00:48, 22 January 2014 (UTC)
Lorentz transformations? RoTFL. Schrödinger equation, an archetypical quantum mechanics, is Galilean invariant. Incnis Mrsi (talk) 07:29, 22 January 2014 (UTC)
Yes, see Wigner's classification. That's how it is done. You'd want something equivalent (using the Galilean group) for non-relativistic QM (but you'll miss out on antiparticles). Or do you want to define quantum particles as billiard balls? YohanN7 (talk) 10:56, 23 January 2014 (UTC)

Explain the symbols!

Wikipedia is about explaining things, right? Making knowledge of a certain subject accessible to people who do not have this knowledge. I think few would disagree. It therefore follows as an absolute given that the explanations be intelligible, a prime example being that symbols and abbreviations be translated into understandable text. However, as often as not such explanations are lacking or cryptic. I am not a physicist but keen to learn about physics and I thought Wikipedia would be a good place to do that. But the main obstacle to that is the number of formulae which use undefined or unexplained symbols. I don't see the point in putting these formulae there if you have to know what they mean beforehand. Examples abound, but take the instance of Lagrangian mechanics:Lagrangian and Action where it says:

"In field theory, the Lagrangian density must be used instead:


What is meant by d? By V? By the calligraphical "L" ? It is not explained! I could have a great time guessing, but life is short and I am derailed here. It should NOT be like that. I think WikiProject Physics should set up a competent task force to find and eliminate this kind of shortcomings. Without such a change, the articles defeat their purpose and become statements by and for those who already know about the subject and therefore do not need them. --Wdanbae (talk) 21:20, 15 January 2014 (UTC)

There is no royal road to understanding (Euclid). Only years of hard work will get you there, and if you don't start as a teenager you may never make it. Xxanthippe (talk) 21:54, 15 January 2014 (UTC).
You have a good point. We do strive to make physics article accessible and part of that is explaining the notation. Most articles at Wikipedia are a work in progress and are incomplete. Maschen has expanded that section in response to this posting and I added a bit more. Hope this helps, --Mark viking (talk) 22:06, 15 January 2014 (UTC)
More specifically: I defined the symbols and made an error in terminology, corrected the error (not too well), then Mark clarified and expanded and the section reads much better.
Please, any formulae with missing or unclear symbols and definitions should just be highlighted at the talkpage. Then someone will fix. We don't need a wikiproject or taskforce just for that. M∧Ŝc2ħεИτlk 22:10, 15 January 2014 (UTC)
@Xxanthippe: your post smacks of elitism. As far as I know, Euclid lived before the age of Wikipedia. The amount of time it takes to learn depends on how well the topic is explained (ask me, I am a teacher). Obscuring an already difficult subject by omitting explanations amounts to sabotage in my view.
@Maschen: I could leave the comment about omitted explanation of symbols on scores of pages; they are all over! Their ubiquity is what drives me to despair. I think it is a serious and pervasive quality problem for the WikiProject Physics. That is why I suggested the task force. But I will leave comments on the individual pages according to your suggestion. I'll make a standard phrase and store on my clipboard.
@Maschen and Mark viking: Thanks for understanding the problem. But please just browse any physics-related WP page and you will almost certainly find unexplained letters and symbols. Wdanbae (talk) 20:50, 22 January 2014 (UTC)
Wdanbae -- The reason that you should complain on the talk page is not just to communicate "There are unexplained symbols on this page!" (which arguably goes without saying) but also to communicate "There are unexplained symbols on this page and it is very important that this problem should get fixed!". Wikipedia editors have limited amounts of time and infinite possible ways to improve articles (making articles clearer, and more accurate, and more comprehensive, and adding diagrams and sources, etc. etc.). So editors have to prioritize. Sometimes there are unexplained symbols but it is not too horrible a problem because 99.9% of the people reading the article can correctly guess what the symbols mean. (Yes, these symbols should be explained, but this is not a terribly urgent problem.) Other times, the symbols are critical for understanding the article and very few readers can understand what they mean -- in which case, explaining the symbols is an urgent priority. If you, personally, are confused by an unexplained symbol, then it is a safe bet that other people are confused too! By posting a message on the talk page, you are telling editors that these unexplained symbols are an especially urgent issue in this particular article, and therefore it is more likely to get fixed promptly. :-D --Steve (talk) 21:21, 22 January 2014 (UTC)
@Wdanbae: It is presumptuous for someone with a total of 61 edits to tell those of us with thousands to "please just browse any physics-related WP page". We have. But there are about 18,000 articles in this project with almost 8,000 cleanup tags, and about 430 people watching this page, many of whom are not very active. We understand the problems very well and are trying to fix them, one edit at a time, and are doing it for free. Perhaps you could help. RockMagnetist (talk) 22:03, 22 January 2014 (UTC)
@RockMagnetist: The intention with the quoted sentence was to say that the phenomenon of unexplained symbols can be found on almost any page, not that Maschen and Mark viking should go over "any page" and correct them. I'd be happy to help in the way I can, although, not being very knowledgeable about the subject, it would be more about identifying problems than fixing them. I also appreciate the "understaffing" problem. However, allegations of presumptuousness and unfavourable comparisons of number of edits are maybe not the ideal way to recruit new hands. Btw, where do the edit numbers show up? Wdanbae (talk) 17:15, 24 January 2014 (UTC)
@Wdanbae: Apparently I misunderstood the intent of your remark, and I apologize for that. We get so many remarks from people telling us what a lousy job we're doing, and I often have to bite back a sharp retort. You can see your edit count here. This page can also be accessed by going to your home page, clicking on "User contributions" under the Tools menu in the bar on the left, and then clicking on "Edit count" at the bottom. RockMagnetist (talk) 17:58, 24 January 2014 (UTC)
@Wdanbae: The article Lagrangian mechanics:Lagrangian and Action contains references to excellent texts like Goldstein and Landau and Lifshitz. There is no reason why you could not have added the notation from those texts yourself instead of demanding that others do it for you. Xxanthippe (talk) 23:15, 22 January 2014 (UTC).
@Xxanthippe: Hasn't WP defeated its purpose if you have to go buy a textbook on the subject in order to understand the article?Wdanbae (talk) 17:15, 24 January 2014 (UTC)
@Wdanbae: Should L be explained? Probably. Should V be explained? Probably. Should d be explained? I'm inclined to say that if you can't recognize an integration measure when you see one, you probably will not get much out of the article in question. Complaining that a calculus-heavy article does not explain basic calculus symbols is a bit like complaining that an algebra-heavy article (polynomial, for instance) does not explain that xy means "multiply x by y". The notation is so frequent that trying to explain it at each use would completely obscure the exposition of the article's subject. Zueignung (talk) 06:06, 23 January 2014 (UTC)
@Zueignung: I agree. The "d" was included by slip of the keyboard, probably as a result of my confusion with the other symbols. Of course there are always borderline cases (like the "dot-above" notation for time derivatives, which is sometimes explained, sometimes not). But the basic symbol repertoire of calculus could be learned in other ways. In contrast, a parameter like "length" or "action" could be symbolized using any of a number of different letters in different articles and not explaining those leaves the reader in limbo, since you cant very well search for the meaning of a single letter in any constructive way.--Wdanbae (talk) 17:15, 24 January 2014 (UTC)
@Wdanbae: Perhaps you haven't noticed yet, but in the mean while I have added wikilinks to the relevant articles explaining what is meant by d and by V. That's the power of linking in an encyclopedia, right? Cheers - DVdm (talk) 08:19, 23 January 2014 (UTC)
@DVdm: Thanks. Great job. I sincerely hope you understand that my frustration is directed against the authors who put ill-defined formulae in the articles, not towards the people who are diligently trying to fix the pages, to which latter category I am confident all of you people above belong.--Wdanbae (talk) 17:15, 24 January 2014 (UTC)
I think your comment is offensive to the editors of the article (I am not among them), who have generally done a good job. As Zueignung says, if you don't recognize an integration measure, then you should study more elementary articles until your understanding is improved. Xxanthippe (talk) 23:15, 24 January 2014 (UTC).


Hi, I have created a new stub article for the U-bit (sic). The cited paper uses the word form "ubit." My reasons for using the hyphenated form are explained at Talk:U-bit. If I have done wrong, please make corrections and forgive my enthusiasm/ignorance. — Cheers, Steelpillow (Talk) 11:06, 27 January 2014 (UTC)

Spin–spin interaction is a red link…

… but there are articles spin-exchange interaction, J-coupling, and possibly others, as well as a tiny section at Angular momentum coupling #Spin-spin coupling. I do not believe one can’t say anything substantial about the interaction between spins of EM-interacting particles in general. Incnis Mrsi (talk) 09:48, 28 January 2014 (UTC)

Spin-spin coupling redirects to Angular momentum coupling. For now why not just redirect to the section Angular momentum coupling #Spin-spin coupling you mention? M∧Ŝc2ħεИτlk 16:41, 28 January 2014 (UTC)

Solar physics

FYI, there is a notice about the article Solar physics at WT:ASTRONOMY -- (talk) 06:41, 30 January 2014 (UTC)

AfC submission

Hello hello! One more to delight your souls. FoCuSandLeArN (talk) 20:51, 26 January 2014 (UTC)

After a short look, it appears ok to me. Could use some copy editing, but the topic seems notable and the references reasonable. — HHHIPPO 21:56, 26 January 2014 (UTC)
I added an afc comment. This article is on a notable topic and as a stub, looks good to me. --Mark viking (talk) 13:03, 30 January 2014 (UTC)
Reviewed and moved to mainspace at Rigidity theory (physics), it could do with better/more categories - fire at will! Roger (Dodger67) (talk) 13:58, 30 January 2014 (UTC)

Exoplanet maximum radius

In the Exoplanet article the Radius section says that cold gas giant exoplanets have a maximum radius due to something to do with pressure. Would someone who understands this please rewrite that sentence to be more explanatory. Astredita (talk) 18:53, 28 January 2014 (UTC)

This would probably be a better discussion for the WikiProject Astronomy. Primefac (talk) 12:08, 29 January 2014 (UTC)
In our every-day experience, when you pile a greater weight upon a substrate, the substrate will be compressed slightly but will be able then to support the greater weight. When the substrate is compressed, the electrons within it must speed up (increase their range of momenta) to avoid violating the Pauli exclusion principle. This results in an increase in pressure. This kind of pressure is called electron degeneracy pressure which must be distinguished from pressure due to heat. When the pressure has increased enough to support the extra weight, the compression stops. As long as the speed of the electrons is small compared to the speed of light, this process is robust.
However, in extreme circumstances such as in very large planets or stars, this compression will become anomalously large. In this case, the electrons are already traveling near light speed and cannot speed up enough to support the extra weight without a much greater compression. This can go so far as to result in the celestial body becoming smaller rather than larger when additional material is added. If you keep adding weight, it will eventually become a neutron star or black hole when the electrons are unable to hold up the weight at any radius. JRSpriggs (talk) 08:06, 30 January 2014 (UTC)
I came here to say "not to worry I've just finished rewriting that section" but when I got here I found your comment JRSpriggs. Thanks for your comment. The main thing I think the article needed was that ordinarily supporting the greater weight is done by coulomb pressure. Astredita (talk) 08:57, 30 January 2014 (UTC)
Sorry, but I think what you call Coulomb pressure is a myth. If there were such a thing, it would be a classical (non-quantum) phenomenon. Since the equations of electromagnetism are linear, reducing all the distances between electrons and nuclei proportionally would just increase the binding energy of the system. Although electrons repel each other and nuclei repel each other, the electrons and nuclei are attracted to each other and that is the predominant effect. Thus there is no classical barrier to bulk matter collapsing to a point.
What happens is, due to the combination of the Pauli exclusion principle and the uncertainty principle, the electrons must move faster when they are closer together. The extra kinetic energy required for this to happen reduces the binding energy. As long as the motion is non-relativistic, the kinetic energy will overcome the potential energy at some point and stop the collapse. JRSpriggs (talk) 09:54, 31 January 2014 (UTC)
Maybe you're right. Maybe my reading of the references is wrong but they talk about coulomb pressure. (Introduction to Exoplanets, Seager and Lissauer, Chapter in Exoplanets, edited by Sara Seager, University of Arizona Press, 2010. and Fundamental Planetary Science: Physics, Chemistry and Habitability, Jack J. Lissauer, Imke de Pater, Cambridge University Press, 16 Sep 2013, page 74.) Astredita (talk) 10:19, 31 January 2014 (UTC)

OK, I've removed what I wrote which for the record was: "Gaseous planets that are hot because they are close to their star or because they are still hot from their formation are expanded by the heat. For colder gas planets there is a maximum radius slightly larger than Jupiter when the mass reaches a few Jupiter-masses because gravity begins to overcome the Coulomb pressure (the electric repulsion between electrons from different atoms) in the planet's core and ionizes the atoms, freeing the electrons, allowing the nuclei to squeeze together more closely. As more mass is added, the radius shrinks because a larger proportion of the planet's atoms overcome the Coulomb pressure. Beyond Coulomb pressure matter is supported by electron degeneracy pressure.[1][2][3]"

  1. ^ Introduction to Exoplanets, Seager and Lissauer, Chapter in Exoplanets, edited by Sara Seager, University of Arizona Press, 2010
  2. ^ Fundamental Planetary Science: Physics, Chemistry and Habitability, Jack J. Lissauer, Imke de Pater, Cambridge University Press, 16 Sep 2013, page 74
  3. ^ Planetesimals To Brown Dwarfs: What is a Planet?, Gibor Basri, Michael E. Brown, (Submitted on 20 Aug 2006)

Astredita (talk) 10:47, 31 January 2014 (UTC)

Merger Proposal

There's a proposal for merging Twinkling and Astronomical seeing, discussion can be found here -- Primefac (talk) 23:15, 31 January 2014 (UTC)