Wikipedia talk:WikiProject Physics/Archive April 2014

Wikipedia talk:Articles for creation/Luis Herrera Cometta

Dear physics experts: Here's another one of those abandoned Afc submissions. Is this a notable physicist, or should the page be deleted as a stale draft? —Anne Delong (talk) 09:13, 30 March 2014 (UTC)

He has some highly cited papers in general relativity and would probably pass WP:Prof on the basis of citations, but as nobody seems interested in pursuing the matter why bother? Xxanthippe (talk) 10:07, 30 March 2014 (UTC).

Well, since only a few editors take the time to look through the Category:G13 eligible AfC submissions, posting here is the only way to find out if anyone is interested. —Anne Delong (talk) 12:54, 1 April 2014 (UTC)

Wikipedia talk:Articles for creation/Forouhi-Bloomer Dispersion Equations as a Basis for Characterizing Thin Films

Dear physics experts: This page has just been submitted at Afc and may be of interest here. —Anne Delong (talk) 14:46, 21 March 2014 (UTC)

Semi-incoherent mish-mash of optical properties of semiconductors. There are cites to the work in Google scholar but I don't think that Wikipedia needs an article of this length and low quality. Xxanthippe (talk) 21:34, 21 March 2014 (UTC).

Well, unlike the abandoned ones I have been posting, this one is newly submitted and has at least one active editor. If it's a notable topic, it will eventually be added to the encyclopedia unless it contravenes Wikipedia policies. Of course, it could be clarified and shortened if appropriate. A lot of articles about complicated subjects start out needing improvement. —Anne Delong (talk) 21:49, 21 March 2014 (UTC)

This is about an approach to modeling the dispersion or refractive index of a semiconductor and is an alternative to approaches like Cauchy's equation and the Sellmeier equation in the case that there is an interband region in the semiconductor. It's used in modeling in the semiconductor industry, but most of the Google hits for this involve papers by Forouhi himself. I did find a secondary reference [1] that compares it to other dispersion models. The article itself looks like a raw dump of a physics paper or handbook article and the complete lack of refs beyond 1988 is suspicious; copyvio needs to be checked for. The article also seems pretty promotional for this particular method and it doesn't mention alternative methods. So, the topic is possibly marginally notable--in my opinion, it meets the AfC 50% survival test--but someone's gonna call WP:TNT on it. --Mark viking (talk) 22:09, 21 March 2014 (UTC)

Wow, nobody will be able to read the full article. It's way too long (for any subject). YohanN7 (talk) 13:00, 1 April 2014 (UTC)

Theory of Dynamic Interactions

One person's theory?! IMHO deletable... --Pjacobi (talk) 09:42, 1 April 2014 (UTC)

Delete as gobbledegook (formally OR). Xxanthippe (talk) 22:05, 1 April 2014 (UTC).

AfC submission - 01/04

Wikipedia talk:Articles for creation/Hidden states of matter. FoCuSandLeArN (talk) 21:19, 1 April 2014 (UTC)

Do give us a valid link. Xxanthippe (talk) 21:41, 1 April 2014 (UTC).

Fixed. --Mark viking (talk) 21:50, 1 April 2014 (UTC)

Is it any different to metastable states of matter? Xxanthippe (talk) 22:02, 1 April 2014 (UTC).

Not that I can tell. in the photoinduced phase transition field, these are usually called nonequilibrium phases or states, or metastable states. Might be a neologism--only 7 hits on GScholar for "hidden state of matter". --Mark viking (talk) 22:19, 1 April 2014 (UTC)

• What about Wikipedia talk:Articles for creation/Rossby Wave Instability in Astrophysical Discs? FoCuSandLeArN (talk) 21:05, 2 April 2014 (UTC)

I noted a possible copyvio and probable COI in an afc comment. --Mark viking (talk) 21:42, 2 April 2014 (UTC)

Heads up at Double-slit experiment‎

Can someone please have a close look at what's going on at Double-slit experiment‎ and Talk:Double-slit experiment‎#de Broglie's wave mechanics. A wp:spa user MPC755 seems to be adding some content with possible wp:SYNTH and wp:UNDUE related problems. Perhaps even wp:FRINGE. - DVdm (talk) 15:03, 4 April 2014 (UTC)

The article is written in a way that invites these sorts of problems, as I just pointed out. Count Iblis (talk) 17:00, 4 April 2014 (UTC)

Vis-viva equation

I think there is an issue regarding the explanation of symbols in Vis-viva equation#Vis viva equation. The symbol v does not denote the speed of orbiting body relative to the central body, but the speed of the orbiting body along its orbit. --Pyrometer (talk) 08:11, 2 April 2014 (UTC)

The article says "In the vis-viva equation the mass of the orbiting body is taken to be negligible in comparison to the mass of the central body.". In this approximation, the two speeds you mentioned are the same. JRSpriggs (talk) 08:30, 2 April 2014 (UTC)

As I understand it, the relative speed between the two bodies is zero at periapsis, because the orbit may be regarded as circular at this point. The velocity is perpendicular to the radius so the orbiter has no component of speed directed to the central mass. Of course there is indeed a component of orbital velocity that is speed in direction of the orbit, but not speed "relative to the central mass".

Or is this just my issue of misinterpreting the English language? --Pyrometer (talk) 09:21, 2 April 2014 (UTC)

I took "relative speed" to mean the magnitude of the relative velocity.

Let the less massive body be #1 and the more massive body be #2. Let x₁ be the position of #1 and x₂ be the position of #2. Let

$\mathbf {x} _{c}={\frac {m_{1}\mathbf {x} _{1}+m_{2}\mathbf {x} _{2}}{m_{1}+m_{2}}}\,.$

I took "relative speed" to mean

$\vert {\dot {\mathbf {x} }}_{1}-{\dot {\mathbf {x} }}_{2}\vert \,.$

And I took "the speed of the orbiting body along its orbit" to mean

$\vert {\dot {\mathbf {x} }}_{1}-{\dot {\mathbf {x} }}_{c}\vert \,.$

But it appears that you thought that "relative speed" meant

$({\dot {\mathbf {x} }}_{1}-{\dot {\mathbf {x} }}_{2})\cdot {\frac {(\mathbf {x} _{1}-\mathbf {x} _{2})}{\vert (\mathbf {x} _{1}-\mathbf {x} _{2})\vert }}\,.$

OK? JRSpriggs (talk) 03:42, 3 April 2014 (UTC)

Hi JRSpriggs!

Yes, my little Problem is the word "relative" in this explanation: "v is the relative speed of the two bodies".

The distance between the two bodies is

$\mathbf {d} ={\frac {(\mathbf {x} _{1}-\mathbf {x} _{2})}{\vert (\mathbf {x} _{1}-\mathbf {x} _{2})\vert }}$.

And I think the wording "v is the relative speed of the two bodies" may lead to misunderstanding:

$\mathbf {v} ={\frac {d}{dt}}({\frac {(\mathbf {x} _{1}-\mathbf {x} _{2})}{\vert (\mathbf {x} _{1}-\mathbf {x} _{2})\vert }})$.

Please excuse my writing, I'm not very familiar to that <math>-stuff

I would be completly happy if that word "relative" is dropped. "v is the speed of the smaller body". (Or some other wording along that line. English is not my native language, so I better don't touch it myself. :-)

BTW I think it might be a good idea to mention it explicitly: The Vis-viva equitation governs orbits and fly-bys, i. e. there is a dominating center mass (at rest) and a moving body with a mass that is much smaller with respect to the mass of the center body. --Pyrometer (talk) 09:14, 4 April 2014 (UTC)

I think that your misunderstanding is relatively rare. Your proposed solution and any other possible solutions would create new problems worse than this one. If you drop "relative", then some people will think (or say) that "speed" means $\vert {\dot {\mathbf {x} }}_{1}\vert$ which is definitely wrong. If (for clarity) we added explicit definitions of the terms as I have done here, then people unfamiliar with the vector notation or with dots and absolute value signs would be lost, and other person's understanding would be impeded. JRSpriggs (talk) 10:30, 4 April 2014 (UTC)

$\vert {\dot {\mathbf {x} }}_{1}\vert$ is exactly $\mathbf {v} _{1}$ in my world. Of course, I assume a center mass at rest, which is an appropiate choice of reference frame in this case. (The idea of accounting for a barycenter common to both bodies seems far fetched and historically not fitting when talking about Kepler orbits)

But that's just my 2 cents. Thanks for commenting on my contribution ;-) --Pyrometer (talk) 12:08, 4 April 2014 (UTC)

I think "radial speed" is the more usual term for the rate of change of separation, I would interpret "relative speed" the way JRSpriggs does above. Djr32 (talk) 13:38, 5 April 2014 (UTC)

Electromagnetic wavelength bands

Am I missing something, or is WP? While editing an article in astronomy, I found the article Radio wave very useful as a link target. Now I would like to have the same for Optical wave (or "Visible wave" or some such), as well, but I do not find any. Each band of the spectrum has its own uses and applications, many in astronomy alone, so it seems reasonable to me that there should be articles for each. What think you all? Evensteven (talk) 20:32, 4 April 2014 (UTC)

Ok, I just saw the Light. Not the title I would have expected necessarily. Maybe a redirect, say from "Visible wavelength" would help. Any other omissions? Evensteven (talk) 20:37, 4 April 2014 (UTC)

At Electromagnetic spectrum there is a table at the top linking to the various articles on conventional frequency bands of electromagnetic radiation. The category Category:Electromagnetic spectrum is also useful for locating the desired articles. In the optical band, we also have Visible spectrum. Visible wavelength is already a redirect to Visible spectrum. --Mark viking (talk) 21:07, 4 April 2014 (UTC)

Thanks. I missed the links in the Electromagnetic spectrum table, but I scanned pretty fast, not really looking for that. The table only has links to the two articles also (visible and radio). I would have expected more - might have looked harder if there had been. Could have sworn I tried "Visible wavelength" with no connect; maybe I had a typo. I guess I really should pay more attention to categories; I've been neglecting them. Sorry for any unwarranted noise. Evensteven (talk) 21:40, 4 April 2014 (UTC)

See also Category:Colors.—Wavelength (talk) 02:16, 6 April 2014 (UTC)

Cosmic age problem

FYI, there's a notice at WT:ASTRONOMY about Draft:Cosmic age problem -- 70.24.250.235 (talk) 04:44, 9 April 2014 (UTC)

Wikipedia talk:Articles for creation/Neutrino mass and the universe

Dear physics experts: Is this old Afc submission about a notable topic? Should it be kept and improved (maybe by changing it to be about the KATRIN project instead of the more general title) instead of being deleted as a stale draft? —Anne Delong (talk) 02:03, 6 April 2014 (UTC)

Hopelessly written article. Delete. Xxanthippe (talk) 02:34, 6 April 2014 (UTC).

Gone; thanks. —Anne Delong (talk) 04:44, 12 April 2014 (UTC)

Trace and tensors

Hi!

It seems like information is extremely sparse when it comes to trace and tensors. At least, I haven't been able to find anything useful. Yet, the physics literature is full of expressions like "traceless", "extracting traces", etc. I have an idea about what things mean, but I don't have enough knowledge to write an article or write a section in trace myself. What I'd like to see is information about

• Trace of general tensors.
• Dependence on metric.
• How to "extract trace", i.e. how to separate the trace part and the traceless part.
• What it is good for, i.e. applications. (I personally have representation theory in mind.)
• Examples.
• More?

I'd like to see a component form formulation instead of some category theory style super-general abstract nonsense, but that's me.

Does anyone agree that we need this? Or do we perhaps have it already? YohanN7 (talk) 10:48, 12 April 2014 (UTC)

Hi YohanN7, it may be that some of the information you seek is in Tensor contraction and Partial trace. Tensor contraction is roughly a synonym for tensor trace. --Mark viking (talk) 15:43, 12 April 2014 (UTC)

Yes, thanks, some, but far from all I have in mind, appears to be in Tensor contraction. I managed to miss that one. YohanN7 (talk) 19:57, 12 April 2014 (UTC)

You might want to look at Talk:Einstein field equations/Archive 1#Trace-free version of EFE. JRSpriggs (talk) 08:26, 13 April 2014 (UTC)

Actually, the first three equations encapsulate the principles of what I am after. Thanks. I have certain linear spaces of (presumably) high rank tensors (no spacetime dependence at this point) that I want to fully reduce into traceless parts. You can see om Mark Vikings talk page what I'm up to. YohanN7 (talk) 11:59, 13 April 2014 (UTC)

LHCb confirms existence of exotic hadrons

The LHCb experiment has confirmed the existence of exotic hadrons - I've added one simple sentence citing Cern's press release, but I'd appreciate if someone knowledgeable about particle physics could synthesisze the sources and update the article accordingly - it was only discovered yesterday, so lets keep enwp on top of current scientific developments! Acather96 (click here to contact me) 13:21, 10 April 2014 (UTC)

Cough cough. Acather96 (click here to contact me) 08:12, 20 April 2014 (UTC)

Elastic recoil detection

Maybe one of you can have a look at this series of edits. They strike me as good-faith edits but they totally mess up the article; I hate to roll them back and it's best if an expert has a look. Thanks. Drmies (talk) 14:28, 25 April 2014 (UTC)

No, it definitely shouldn't be reverted. A new user has massively expanded the article, which previously was little more than a stub. All of the content looks reasonable. The mess can be fixed, but it's more important that we keep the content, and don't drive away new editors. Djr32 (talk) 22:05, 25 April 2014 (UTC)

This article has the look of a possible copyvio. RockMagnetist (talk) 22:26, 25 April 2014 (UTC)

Quite frankly, the new version is a dreadful mess, well below the standards expected in Wikipedia. The sensitivities of new editors do not get precedence over Wikipedia's standards of quality. I support reversion. Xxanthippe (talk) 22:31, 25 April 2014 (UTC).

Quality improves in multiple directions, not all simultaneous. Addition of reasonable, accurate content is one. Writing presentation is another. The latter is a mess right now, but the stub was short and lacked the added content. The stub was also much better written. As a starting point, I will restore all the stub's verbiage and install it as the lead, which gives the article back any virtues that it once had. The stub was much more like a lead than anything else anyway. I'll also try to touch on a couple of other details within the new additions to get at some of the most glaring mess. I'm not a physicist; I just have certain knowledge in the sciences, and this article is mostly out of my depth technically speaking. Watch what I do and make any technical corrections necessary. But I'm usually able to get close enough to the mark to make progress towards recasting content into a better presentation. My commitment to this one has limits, but hopefully I can position it well enough to enable others to step in also. Evensteven (talk) 23:17, 25 April 2014 (UTC)

Just a note: I don't think the new editor is a native English-speaker. Evensteven (talk) 23:38, 25 April 2014 (UTC)

Suggesting that continued discussion be taken over to Talk:Elastic recoil detection#Initial discussion. Evensteven (talk) 18:25, 26 April 2014 (UTC)

To all those who've taken this on: Good work! It's good to see that we can take the work of an enthusiastic and knowledgeable new editor and combine it with WP-expertise to create a much improved article. Djr32 (talk) 21:50, 28 April 2014 (UTC)

Royal Society journals - subscription offer for one year

I'm delighted to say that the Royal Society, the UK’s National Academy for science, is offering 24 Wikipedians free access for one year to its prestigious range of scientific journals. Please note that much of the content of these journals is already freely available online, the details varying slightly between the journals – see the Royal Society Publishing webpages. For the purposes of this offer the Royal Society's journals are divided into 3 groups: Biological sciences, Physical sciences and history of science. For full details and signing-up, please see the applications page. Initial applications will close on 25 May 2014, but later applications will go on the waiting list. Wiki at Royal Society John (talk) 03:04, 29 April 2014 (UTC)

Nonsense article on time correction

User Magravat seems to be putting a lot of work in an article about his own "research" at Wikipedia talk:Articles for creation/Time correction. I have no idea how to let him know that it's not going to work. To me it looks like extreme nonsense. Two reviewers already rejected it but I don't think they really knew what it is about. Does someone know how to prevent this user wasting his time here? See also Wikipedia talk:WikiProject Physics/Taskforces/Relativity#Article on time correction - DVdm (talk) 14:51, 28 April 2014 (UTC)

I don't think AfC has a "this is never going to be accepted" option. Has anyone tried posting a message on Magravat's talk page to say just that? Djr32 (talk) 17:09, 28 April 2014 (UTC)

Frankly, I wouldn't know how to gently break the news... - DVdm (talk) 17:42, 28 April 2014 (UTC)

I've posted this: [2]. You can decide for yourself whether this is gently breaking the news or not... Djr32 (talk) 21:47, 28 April 2014 (UTC)

Thanks, quite gentle. I hope that this will help, although I have some doubts: after your message (23:46, 28 April 2014) he already made two more edits (00:23, 29 April 2014 and 00:36, 29 April 2014 )... - DVdm (talk) 10:24, 29 April 2014 (UTC)

Shrug... Well, if s/he really wants to spend time writing about this stuff on WP, I'd rather it was going in an AfC article that will never be accepted rather than adding to the clean-up workload on existing articles. Djr32 (talk) 12:04, 29 April 2014 (UTC)