Wikipedia talk:WikiProject Physics/Archive May 2011

This is an archive of past discussions on Wikipedia:WikiProject Physics. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

IP adding material to cosmology articles.

An IP editor, 177.24.107.124 (talk · contribs · WHOIS), has just added the same paragraph to dark energy and physical cosmology claiming that a Brazilian professor recently demonstrated the origin of dark energy. If someone with a cosmology background could take a look at this, that'd be helpful. My first thought is that it's self-promotion of an as-yet non-notable primary source, but I don't follow cosmology journals. --Christopher Thomas (talk) 15:42, 23 April 2011 (UTC)

On a slow week there will be at least 5 articles on the gr-qc arxiv, that claim to have a new explanation for 'Dark energy'. It is doubtful that any of them deserve mention on wikipedia. Since the source of this claim was an article in crackpot journal Progress in Physics, I've reverted both additions.T R 16:24, 23 April 2011 (UTC)

There is continued spamming of this article leading to edit warring. Some extra attention at Cosmology and Cold Big Bang would be helpful. Tim Shuba (talk) 02:00, 5 May 2011 (UTC)

Signpost article

A few of you have been approached about being interviewed for Wikipedia Signpost's article about WikiProject Physics. On one hand, I realize that this is our equivalent of a student newspaper, so not terribly high on peoples' priority lists. On the other hand, I've answered interview questions, and I'm probably not everyone's first choice for ambassador of WikiProject Physics. It's worth spending a few minutes to get a few more responses on the interview page, as an amusing diversion if nothing else.

I was contacted by Mabeenot (talk · contribs), and Thomas888b (talk · contribs) also seems to be involved with this article. They can presumably answer further questions. If I understand correctly, any of us can respond (I was asked to suggest more people to interview). If I'm reading the signpost's queue correctly, "publication" happens on May 2nd, so I figured I should send a ping while it's still the weekend. Enjoy! --Christopher Thomas (talk) 21:59, 30 April 2011 (UTC)

The interview can be found at Wikipedia:Wikipedia Signpost/2011-05-02/WikiProject report. Both CT and I responded. Read it at your leisure. Headbomb {talk / contribs / physics / books} 05:43, 5 May 2011 (UTC)

Fringe theory?

Please examine the edits of Gordonben (talk · contribs). They add a new theory of dark matter based on a single publication in a journal with no impact factor (yet), which is why my reverts. However, the user reverts back, and thus a check by another editor is required. Materialscientist (talk) 13:31, 5 May 2011 (UTC)

They're adding this link to quite a few articles, as far as I can see. I've put a non-templated warning on their talk page about link-spamming and edit-warring, and attempted to explain to them that if an addition of theirs is removed, they should start a talk page thread rather than re-adding it themselves. --Christopher Thomas (talk) 21:12, 5 May 2011 (UTC)

Expert attention for Micro-channel plate article?

I'm new to Wikipedia and don't really know what I'm doing yet, so was hoping for a bit of guidance on this issue.

I saw the Microchannel plate detector article was requesting expert attention, so I thought I might put my hand up for that. Is there anything I'm meant to do to clarify that I am an expert? Or enough of an expert?

I work with this equipment regularly, so I have some familiarity with them. I also have (hard-copy) manuals available at my disposal, which contain a lot of good information. These are probably not readily available to other people though. Is there some sort of rule to say a reference must be sufficiently readily available to others that they are able to check its validity or something?

Also, what exactly is required for the article? 'Expert attention required' is a bit vague. Are there any particular areas that should be focused on? Any specific issues that need to be addressed?

Any help would be greatly appreciated.

129.96.220.171 (talk) 10:23, 6 May 2011 (UTC)

I've taken a quick look, and I'm not sure why the template is there either. The article's talk page (under the "discussion" tab) might contain comments, but check timestamps to make sure that the comments in question are about a recent version of the article.

As far as I can tell, the article is fundamentally sound, but could perhaps use a figure or two (for chevron and z-profile channel stacks, and maybe in the section at the top describing the cascade process in the first place). It's also not a bad idea to read through it in its entirety to see if anything inaccurate got put in that hasn't been corrected (a good thing to do with pretty much all articles, actually).

Good to hear that you're interested in helping! --Christopher Thomas (talk) 17:22, 6 May 2011 (UTC)

Problematic edit at inflation (cosmology)

If somebody has time and energy, could they have a look at this series of edits. It adds some stuff that should be covered in the article, namely that inflation has been the subject of criticism by some theoretical heavy weights such as Penrose. It however does so in a very POV and argumentative way. I considered reverting, but I think it would be best if the new section is editted to convey the same information in a more neutral tone, including some of the counter arguments, etc. I do not really have time to dive into this now, so hopefully somebodyelse has.T R 12:16, 9 May 2011 (UTC)

Another article that seems to be based only on work by Fedosin

I think this article Gravitational induction seems to have many of the same issues raised at Wikipedia:Articles_for_deletion/Strong_gravitational_constant_(2nd_nomination) , but in any case it would benefit from having someone who knows more about physics than I do take a look. betsythedevine (talk) 13:22, 9 May 2011 (UTC)

Vetting needed at Special relativity.

There were some minor changes to the actual equations themselves but these seem legitimate based on a quick going over; mostly adding beta notation, understandable as it's used later in the article, and being accurate about conditions. On the actual like-for-like change in math formatting i don't don't know what is the prefered form. ChiZeroOne (talk) 22:49, 9 May 2011 (UTC)

I asked the IP to explain his 13 edits on the talk page. If there is no problem the edits can be restored. Xxanthippe (talk) 23:02, 9 May 2011 (UTC).

Xxanthippe, I just hope you're not "biting the newcomers", i.e. making new editors feel unwelcome. When a (possibly) new editor does some time-consuming and good-faith and reasonably-on-the-mark edits, you should undo them only if you're 100% sure they make the article noticeably worse. Not just because you're less than 100% sure that they make the article better. Reversions are usually taken as mean-spirited, even when you say it's not. And don't forget to leave a user-page message, not everyone knows how to find the edit summaries. Just my opinion! :-) --Steve (talk) 01:17, 10 May 2011 (UTC)

I don't want to bite anybody. If edits as substantial as these are made (particularly by anons) is is customary to expect an explanation for them. If that is fine then the edits can be restored. Let us not rate style over substance. Further, the anon is scarcely a newbie, having edited since January 2008. Xxanthippe (talk) 02:24, 10 May 2011 (UTC).

IP can be shared; in any event, I'd have given more substantial reason to revert than “Please justify your edits” or, lacking one, asked for explanation before reverting. (In this case, MOS:MATH#Choice of type style applies.) ― A. di M._plé^dréachtaí 13:10, 10 May 2011 (UTC)

I have done a preliminary check of the changes. The annonymous editor made two sets of changes:

He added alternate formulations of "sqrt(1-v^2/c^2)" showing them as "sqrt(1-β)".
He rewrote dx/dt as dx/dt, presumably implying that "d" is a differential operator rather than a variable - a mute point since it has been argued (by amongst others, Heaviside) that the operator is "d/dt".

I am marginally in favour of letting the revert stand, but like other editors, am unhappy because of the way it was done.Martinvl (talk) 14:22, 10 May 2011 (UTC)

Article - Metric System

I have added the article Metric system to the Physics workgroup portal - I would like feedback as to whether this article is suitable for such an inclusion - I know that the article International System of Units is included - the article Metric system examines the underlying rationale of both the SI and cgs systems in parellel. If this article is appropriate, would someone please assess it?

Comments? Martinvl (talk) 09:02, 10 May 2011 (UTC)

Assessed.T R 15:09, 10 May 2011 (UTC)

Merge of "C parity" and "C-symmetry" pages + addition of content

There should be one page for these two. C-symmetry should be added to the C parity page, as it is a symmetry related to the application of the charge conjugation operator, defined on the C parity page.

Furthermore, a development of the definition of the charge conjugation operator would be be useful. —Preceding unsigned comment added by Aceoftrades (talk • contribs) 06:29, 12 May 2011 (UTC)

I think that it would be better to do the merger the other way — add "C parity" to "C-symmetry". "C parity" is a confusing name because it makes me think of CP rather than C. JRSpriggs (talk) 23:14, 12 May 2011 (UTC)

Help needed on talk:superbradyon

There's an edit war going on for superbradyon. Currently, it looks like meat/sockpuppets of Mr. Gonzales are trying to keep the article from being redirected to his article. I think a suitable end would be to redirect it to the target that was selected in the AFD three years ago, Lorentz covariance#Lorentz violation, but someone with a knowledge of particle physics would need to do so, if there's any merit to the merge (anyway). --Izno (talk) 21:50, 13 May 2011 (UTC)

Nomination for deletion of Superbradyon

Someone has sent Superbradyon to AfD for deletion. 184.144.163.181 (talk) 05:07, 14 May 2011 (UTC)

There's also an AN/I thread about this. --Christopher Thomas (talk) 07:39, 14 May 2011 (UTC)

Vetting needed on "stellar core collapse" draft article

I am writing a fairly substantial article on stellar core collapse. Because of the scope of this topic, its technical nature in parts, and its connections to numerous fields (physics, astronomy, cosmology) I would like to ask in advance for any users prepared to review it for accuracy, omissions, and "latest research findings" before I move it to mainspace. Of particular interest to this Wikiproject, it contains considerable detail on quantum interactions, particle production/annihilation, nucleosynthesis processes, and core collapse models including collapse to degenerate matter, neutrino activity and the like.

Would anyone interested or knowledgeable please let me know on my talk page. Estimated timeline - not less than 3 weeks and maybe more as I have a lot left to do before I would feel I've done "all I can".

Thanks for any help you can offer!

FT2 ^{(Talk | email)} 00:41, 17 May 2011 (UTC)

Cleanup list is stale

Very many of the articles listed at Wikipedia:WikiProject Physics/Cleanup listing as needing wikification, have in fact already been wikified. Can some friendly bot regenerate this listing and bring it up to date? It's now 15 months old. --Wtshymanski (talk) 17:04, 18 May 2011 (UTC)

User:Orphadeus

FYI, there is a notice at WT:AST about Orphadeus (talk · contribs) and an edit/revert war going on. 65.95.13.213 (talk) 04:58, 19 May 2011 (UTC)

Luis González-Mestres

Could someone with knowledge on the subject (particle physics) take a look at this BLP article and try to sort it out? Beyond My Ken (talk) 20:13, 23 May 2011 (UTC)

Improved measurement of the shape of the electron

Hopefully this is of interest. There is an overview (magazine coverage) here and the actual research article is here. Unfortunately I have not been able to find a free (self-published?) version of the research. ---- Steve Quinn (talk) 01:24, 26 May 2011 (UTC)

I think "Nature" has a better layman's explanation of this latest measurement here. ---- Steve Quinn (talk) 02:00, 26 May 2011 (UTC)

See Electron electric dipole moment. Someone has already updated it with the new upper bound. --Steve (talk) 03:39, 26 May 2011 (UTC)

What does this mean? I was under the impression that the electron was a point particle or perhaps a loop of superstring so small that it is experimentally indistinguishable from a point. So how can it have a shape? How can one talk about blowing it up to the size of the solar system, if it has no diameter?

What would it mean for it to have an electric dipole? That the point where the electric charge is located is not the same as the point where the mass is located? I could see it having an electric quadrupole. JRSpriggs (talk) 21:46, 26 May 2011 (UTC)

It is believed to be a point particle, which means it shouldn't have an electric dipole moment. At a glance, this seems to be yet another experiment confirming that to greater precision (placing a smaller upper bound on its dipole moment). I'm not quite sure how nonzero values are generated in the variant models mentioned at electron electric dipole moment. The news, such as it is, seems to be that a few of these alternate models are excluded by the new results (or at least would have to be modified to predict a smaller electric dipole moment). --Christopher Thomas (talk) 23:37, 26 May 2011 (UTC)

The Standard Model predicts a electric dipole moment (albeit very small), parallel to the spin (or maybe antiparallel). We all know that a point particle can have a magnetic dipole moment (see electron magnetic dipole moment), why is it so surprising that a point particle can have an electric dipole moment too?

The "shape of an electron" is a ridiculous way to describe this IMO, the authors or editors just wanted to make it sound less technical. :-) --Steve (talk) 23:47, 26 May 2011 (UTC)

I stand corrected, then. I'd known about magnetic dipole moment (charge and intrinsic angular momentum will do that); thanks for the pointer about the electric moment.

It might be worth editing the electron electric dipole moment article to make it clear that a nonzero value is expected. As-is, it gives an upper bound, with the implication (to me, anyways) that a value of zero would be consistent with the model. --Christopher Thomas (talk) 00:08, 27 May 2011 (UTC)

OK I did. :-) --Steve (talk) 02:06, 27 May 2011 (UTC)

Pauli's Exclusionary Principle

If one searches for Exclusionary Principle one gets pages of law articles. Even on the Pauli page there's nothing that's easy to find. It is, however, an expression that people run into without having sufficient background to place it. Could someone create a search path to some existing page or create one? <I don't know enough to DIY.> THANKS 99.11.160.111 (talk) 13:00, 26 May 2011 (UTC)

It's usually called the exclusion principle, without the -ary. ― A. di M._plé^dréachtaí 19:55, 26 May 2011 (UTC)

Need help at Talk:Center of gravity

I'm discussing this new article with a new editor, and I don't think I'm getting through to them. Can someone else please chime in? Thanks, Melchoir (talk) 01:17, 25 May 2011 (UTC)

ping Melchoir (talk) 07:29, 27 May 2011 (UTC)

I'm still on semi-sabbatical due to editing fatigue and RL concerns, sorry. --Christopher Thomas (talk) 08:39, 27 May 2011 (UTC)

Please be more specific, so we do not have to read the entire talk page and revision history of the article to figure out what the dispute is about! JRSpriggs (talk) 21:10, 27 May 2011 (UTC)

Well, it's morphed a bit over the past couple days, but basically, one user (GenKnowitall) is advocating a particular formulation of a center of gravity concept, namely the center of gravity of an extended body relative to a given point. This is a center from which the body's gravitational field, measured at the given point, is given by a 1/r^2 law. It is mostly referred to as Symon's definition in the talk page.

I (Melchoir) have been arguing that other authors' definitions conflict with Symon's definition. In particular, it is more common to define a center of gravity relative to an external gravitational field. In Feynman's formulation, this is a center from which the total gravitational torque on the body due to the external field is zero. There are also other, inequivalent formulations of a center of gravity of a body in a field. The most notable is a weighted-average definition.

I provided citations for the various treatments in the article, culminating in this version. GenKnowitall reverted my changes to this version, which contains only the Symon definition, on the grounds that I hadn't proposed the changes on the talk page first. Netheril96, Martinvl, and Parejkoj have weighed in on the talk page. Within the last hour, Sbyrnes321 has reverted back to my version.

There's an underlying question of the extent to which these generalized centers of gravity are useful concepts, and I think disagreements on that point are fueling the fire. Melchoir (talk) 23:10, 27 May 2011 (UTC)

I think it would help if you could provide formulas for the other definitions, similar to that for the Symon definition. I think that would make them look more legitimate, especially since some of the wording is not exactly crystal clear. JRSpriggs (talk) 23:38, 27 May 2011 (UTC)

Agreed! I'll probably be able to do that later today. Melchoir (talk) 23:44, 27 May 2011 (UTC)

Electromagnetic momentum and angular momentum

I searched but didn't find articles on the density and flux of electromagnetic momentum and angular momentum. Do those article exist?--Netheril96 (talk) 12:45, 28 May 2011 (UTC)

Maxwell stress tensor includes electromagnetic momentum density. Poynting vector also mentions it in the section Poynting vector#Poynting vector and radiation pressure. Not sure about the other things. :-) --Steve (talk) 17:09, 28 May 2011 (UTC)

In the Electromagnetic stress-energy tensor, the spatial-spatial components (i.e. the Maxwell stress tensor) are the flux (movement) of linear momentum. The spatial-temporal (or temporal-spatial) components (i.e. the Poynting vector) are the density of linear momentum or, equivalently, the flux of energy. The temporal-temporal component is the density of energy. (You may have to multiply by a power of c to get the units right in these equivalences.)

For i component of the angular momentum, use

\varepsilon _{ijk}x^{j}T^{k\nu }\,

where T is the stress-energy tensor, x is the position vector, and

\varepsilon _{ijk}

is the Levi-Civita symbol. JRSpriggs (talk) 02:17, 30 May 2011 (UTC)

That isn't in the current article. Besides, electromagnetic angular momentum still deserves a separate article, just like electric field and magnetic field have their own article even they are just components of a common field tensor.

And I'm not here to ask questions about electromagnetism. I'm here to find out whether new article needs writing.--Netheril96 (talk) 09:01, 30 May 2011 (UTC)

What names will you use for the articles which you are proposing to write? Some may deserve full articles and some may merely be made into redirects to existing articles. JRSpriggs (talk) 04:28, 31 May 2011 (UTC)

Angular momentum of electromagnetic field.--Netheril96 (talk) 07:03, 31 May 2011 (UTC)

More eyes/opinions needed at Big Bang