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[edit] review please

Can someone look at DNA Phantom effect and tell if it is real or a hoax? Thank you. RJFJR (talk) 20:23, 4 December 2009 (UTC)

I've had a look, and it looks like an obscure and nonsensical fringe theory, kept alive as someone is trying to make money off it, so I've put it up for deletion at AfD. --JohnBlackburne (talk) 14:13, 12 December 2009 (UTC)

[edit] Good article Nominations

There are currently three physics articles that have been nominated for GA and are awaiting review:

Stephen Hawking (a top priority article for this project!)
Geothermal power
Kazuhiko Nishijima

If anybody here has some time to spare please consider reviewing one of these articles. Review GAN's does not require any special privileges on wikipedia so anybody can help out. Just be sure to review the guidelines at WP:GAN. Some experience with GA process is useful though, for example having worked on an article that has passed GAN. Even if you don't have time to do a complete review, it can still be very helpful if you can leave some comments on these nominees. Remember that this process can only work if people with suitable background actually participate! Thanks. TimothyRias (talk) 09:03, 15 December 2009 (UTC)

[edit] Emission spectra and code

(Previous thread: here)

I've been busy enough at work that it's becoming clear I won't be improving my spectrum plotting script any time soon. Instead, I've put the code on-wiki at User:Christopher Thomas/spectrum script v1. By all means copy and modify this code if you would find it useful to do so! --Christopher Thomas (talk) 17:41, 16 December 2009 (UTC)

[edit] Tritium

I found the sentence helium-3 has a very large cross section for the (n,p) reaction with thermal neutrons in the tritium article and a IP changed it to helium-3 has a very small cross section for the (n,p) reaction with thermal neutrons. Ha anybody a clue which of the two versions is right? Thanks.--Stone (talk) 10:46, 17 December 2009 (UTC)

I would say very high as scattering cross section of He-3 for thermal neutrons is 5330 barn[1] whereas that for comparable light nuclei is ~0.1 barn.[2]
SPat ^talk 11:10, 17 December 2009 (UTC)

Thanks for the quick help! Materialscientist has corrected it.--Stone (talk) 06:11, 18 December 2009 (UTC)

[edit] Copyright concerns related to your project

This notice is to advise interested editors that a Contributor copyright investigation has been opened which may impact this project. Such investigations are launched when contributors have been found to have placed copyrighted content on Wikipedia on multiple occasions. It may result in the deletion of images or text and possibly articles in accordance with Wikipedia:Copyright violations. The specific investigation which may impact this project is located here.

All contributors with no history of copyright problems are welcome to contribute to CCI clean up. There are instructions for participating on that page. Additional information may be requested from the user who placed this notice, at the process board talkpage, or from an active CCI clerk. Thank you. --Moonriddengirl ^(talk) 17:40, 19 December 2009 (UTC)

In looking through his copyright violations, I've found that he has a tendency to both

Cite the sources he stole from, and
Steal from the arXiv.

He's also taken things from Google Books and from Springerlink. Anyone interesting in helping out can join in at Wikipedia:Contributor copyright investigations/Henry Delforn. Ozob (talk) 09:21, 21 December 2009 (UTC)

Followup: While most of the affected articles were math related, a good portion were physics. Many article have been tagged with copyvio and are subject to being deleted in less than a week. You can find a list of the tagged physics articles at Wikipedia:WikiProject Physics/Current activity in the copyright problems section.--RDBury (talk) 08:19, 24 December 2009 (UTC)

Um, if he's citing the sources then it can hardly be theft, can it? --Michael C. Price ^talk 21:15, 27 December 2009 (UTC)

The problem is direct quotations without quotation marks. --Steve (talk) 23:01, 27 December 2009 (UTC)

[edit] Introductory physics

FYI, Introductory physics has been prodded for deletion.

70.29.211.163 (talk) 05:24, 22 December 2009 (UTC)

[edit] An Exceptionally Simple Theory of Everything

An Exceptionally Simple Theory of Everything got some needed reworking. It would be nice if others could check it for completeness and neutrality.--Verbapple (talk) 00:31, 23 December 2009 (UTC)

The theory was a flash in the pan which has since fizzled out. Perhaps the article is no longer needed. Xxanthippe (talk) 04:33, 23 December 2009 (UTC).

Still worth keeping IMO, as it did legitimately generate press (giving it at least minimal notability). As long as it isn't given undue weight on other pages, I don't see why it wouldn't be kept? --Christopher Thomas (talk) 08:34, 23 December 2009 (UTC)

[edit] Infraparticle up for deletion-- needs expert eye

Infraparticle is up for deletion possibly only because it is so badly written that us non-high-end physics types can't tell whether it is just a bunch of physico-babble. We are aware that there is a real reference to such a thing, but we can't tell whether this article is actually about it. Some tough love from experts is needed. Mangoe (talk) 14:44, 26 December 2009 (UTC)

[edit] Extensive edits of physics articles by banned user

There appears to be a banned user creating multiple accounts serially, mostly editing BLP and physics articles. Their accounts may include Verbapple (talk · contribs), Afteread (talk · contribs), and Miles1228 (talk · contribs), all currently blocked. The edited articles include Bogdanov affair, Marcus du Sautoy, Edward Witten, Antony Garrett Lisi, An Exceptionally Simple Theory of Everything, Andrew Wiles, Elliot McGucken, Pythagorean triple, Lee Smolin, Leonard Susskind, Steven Weinberg, The Elegant Universe, Frank Adams, Jan Hendrik Schön, John C. Baez, Theory of everything, Peter Woit, Standard Model, Alexander Grothendieck, The Story of Maths, Kent Hovind, Luboš Motl, and several others. The banning policy encourages but does not require editors to enforce the ban:

"Anyone is free to revert any edits made in defiance of a ban. By banning a user, the community has decided that their edits are prima facie unwanted and may be reverted without any further reason. This does not mean that obviously helpful edits (such as fixing typos or undoing vandalism) must be reverted just because they were made by a banned user, but the presumption in ambiguous cases should be to revert. When reverting edits, care should be taken not to reinstate material that may be in violation of such core policies as neutrality, verifiability, and biographies of living persons. Users who reinstate edits made by a banned editor take complete responsibility for the content by so doing."

Since there were a lot of edits in this case, reversion help would be appreciated. Thanks. Golumbo (talk) 09:22, 27 December 2009 (UTC)

Any chance of a pointer to where all of this was decided? (And, critically, when it was decided?) I had a quick look through one or two of the articles listed above, didn't see anything out of the ordinary, though none of them are really in my area. Djr32 (talk) 12:36, 27 December 2009 (UTC)

See: Wikipedia_talk:WikiProject_Mathematics#Strange_edit_summaries_by_Golumbo. BeforeAfteread (talk) 02:16, 29 December 2009 (UTC)

[edit] Stimulated emission

Can someone check that the statement in the lead at Stimulated emission, that the second photon is created with the same phase, frequency, polarization, and direction of travel as the original. is true? I suspect that it might only be true macroscopically, in that these contributions are reinforced by constructive interference and the others destructively cancel, but am not sure. --Michael C. Price ^talk 10:09, 27 December 2009 (UTC)

AFAICT they have the same wave vector and polarization; essentially, the occupation number of photons in that state increases by 1. Not 100% sure about that, though. ― A._di_M.^{2nd Dramaout} (formerly Army1987) 12:32, 27 December 2009 (UTC)

A simple dumbed down explanation goes as follows. The amplitude A of the process is obtained from some matrix element A = <out|M|in>, where |in> represents the atom in the excited state and one incident photon and |out> is the atom in the ground state and two photons. The stimulated emission effect is the fact that A peaks for the additional photon in |out> in the same state as the original photon. To see without doing any calculations why this is the case, consider the reverse process where the |out> state is the initial state and the |in> state is the final state. So, we have two incident photons and an atom in the ground state, the final state is the atom in the excited state and one photon. The amplitude of this process is, of course, the complex conjugate of the amplitude of the original process, so the absolute value squared is the same.

Now, if you have two incident photons, then either one can interact with the atom, bringing it in an excited state and the other just moves along. So, you have two contributions to the final state, but the photon in the final state can be in a different state. The amplitude for the final state photon to be in some given state is then obtained by taking the inner product of both contributions with that given photon state. If we keep the state of one of the incident photons the same and we look at amplitude for the final state photon to be in the same state then this is clearly maximized if we choose the state of the other incident photon the same as the other photon. Count Iblis (talk) 15:55, 27 December 2009 (UTC)

Stimulated emission is not so much a physical process as a result of using probability amplitudes rather than probabilities when considering particles with Bose–Einstein statistics. The "amplification" is due to the photons (the original photon or photons and the stimulated photon) being indistinguishable, so that you get cross-terms when multiplying the amplitude by its complex conjugate to get the probability. Thus they must have the same properties. (But make sure that the set of properties being considered is a commuting set of observables.) JRSpriggs (talk) 15:59, 27 December 2009 (UTC)

Well, neither the original photon nor the emitted photon can have an exact frequency or direction or phase (by the uncertainty principle). Even a "single-mode" laser has finite linewidth. Both photons have some distribution of frequency and direction and phase. And I think the more distributions overlap, the more stimulated the emission is. The standard formula for stimulated emission rate assumes the distributions coincide. But if the photon quantum states have 99% overlap instead of 100% overlap, the stimulated emission rate will only be 1% lower.

I think people don't usually think of stimulated emission as being related to interference. The main (microscopic) explanations I've heard are

Properties of creation and annihilation operators for photons (or Bose-Einstein statistics for photons)
(Classical) light shakes (classical or quantum) electron, then electron radiates light. (e.g. semiclassical version fully-classical version)

Maybe there are other explanations involving interference, but I haven't heard them.

I think the statement in the lead that you quote is fine. --Steve (talk) 16:05, 27 December 2009 (UTC)

The lead implies that, if an isolated excited atom is struck by a photon, the emitted photon always departs in the same direction as the original photon. Is this correct? --Michael C. Price ^talk 06:06, 29 December 2009 (UTC)

I say yes. It sounds like you're worried that stimulated emission is like second-harmonic generation where the light goes a certain direction because the different locations add in phase for one light direction and out of phase for other directions. For example, if you use a tiny second-harmonic-generating-crystal much smaller than the wavelength of light, the second-harmonic light would radiate in all directions, because it's so small that the whole crystal is in phase for any direction. Stimulated emission isn't like that. You can make a laser where all the stimulated emission occurs in a tiny area, much much smaller than the wavelength of light, and it doesn't affect how sharp the beam is.

(I haven't heard of that exact experiment with one atom and one free-space photon. Experiments like that usually have a cavity, so there's a priori only one photon direction that the atom can easily radiate into.) --Steve (talk) 07:02, 29 December 2009 (UTC)

Your parenthetical comment suggests that it remains possible that it is more the cavity that enforces the direction of emission, rather than the absorption/stimulated emission per se.--Michael C. Price ^talk 16:47, 31 December 2009 (UTC)

The role interference plays in this is that the total amplitude is so large because all the photons interfere constructively (which is what JRSpriggs said in a more precise way). (Another thing I've heard—but I don't thing it was intended to be any more than hand-waving—is that if the light shakes the electron in phase with its current motion you get absorption, otherwise you get emission. The QM analogue of this, of course, only applies if you have three eigenstates of H such that <3|H|3> − <2|H|2> = <2|H|2> − <1|H|1> and now you're in the state |2>, otherwise there's no way you have both a significant chance of emitting and of absorbing depending only on relative phases (I guess).) ― A._di_M.^{2nd Dramaout} (formerly Army1987) 17:07, 27 December 2009 (UTC)

The lead implies that, if an isolated excited atom is struck by a photon, the emitted photon always departs in the same direction as the original photon. Is this correct?

It should be clear that this is not correct. Just compute the differential cross section for this process. All you'll find is that the amplitide is maximized when the emitted photon is in the same state as incident photon, which can be easily understood per the reasoning involving the inverse process given by me above, which implicitely uses Bose-Enstein statistics for photons. Count Iblis (talk) 01:10, 1 January 2010 (UTC)

Yes, it seemed to me that this was not correct, and that therefore the lead needs modifying. How this ties in with JRSpriggs answer is not clear to me. The sense I'm getting from all the replies is that bosonic clumping makes the additional photon more likely to be emitted in the same direction, but not a 100% likely (i.e. a certainty). However Spriggs indicates this might be 100%, and his argument seems interesting, so I'm still not clear. --Michael C. Price ^talk 07:58, 1 January 2010 (UTC)

It is certainly possible for the emitted photon to be in a different state than the given photon, but in that case the presence of the given photon does not stimulate the emission, that is, the probability of the emission in that state is the same as if the given photon were not present. This is the same conclusion as one gets from Count Iblis's argument. JRSpriggs (talk) 20:13, 1 January 2010 (UTC)

[edit] Tensors on Wikipedia

There is a thread that might benefit from input from the physics project at WT:WPM#Tensors on Wikipedia. Sławomir Biały (talk) 13:47, 29 December 2009 (UTC)

[edit] Wall of Recognized Content (WoRC)

The Wikipedia:WikiProject Physics/Recognized content page is now automatically updated by a bot. This means less trouble for us, and up-to-date goodness for us and others. Maybe someone could incorporate this into the physics portal. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 05:06, 31 December 2009 (UTC)

[edit] Particle in a box

Previously posted at WikiProject History of Science

I've been doing quite a lot of work on the Particle in a box article, trying to make it more descriptive and less mathematical. However, consensus seems to be that we need a history section. I could come up with some very general waffle about the early days of quantum mechanics, but if anyone can help with specific details about who first developed the particle in a box model, then I'd be very grateful. Thanks, Papa November (talk) 17:19, 2 January 2010 (UTC)

[edit] Talk:Rydberg matter

There a potentially 'ticking-time bomb' situation developing at Rydberg matter. An editor with a COI wrote a good chunk of the article, and another suggested that the article does not reflect mainstream physics on the issue. Extra pairs of eyes on the page would be nice. It's relatively civil now, but the tone of the discussion leads me to think that it could get ugly soon. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 02:07, 3 January 2010 (UTC)

Yes, the article looks stuffed full of actual or potential POV, OR and ownership issues. Xxanthippe (talk) 02:30, 3 January 2010 (UTC).

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