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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)
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)
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)
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)
Amidst the usual cruft, someone posted a very interesting question (at Talk:Big Bang#Underlying Assumptions). The question is about what the exact domain of applicability was of the proof that an expanding universe must have expanded from a singularity. This is way out of my league to address, but I seem to recall that there were at least a couple of GR specialists among the WP:PHYS crew. -- Christopher Thomas ( talk) 04:03, 6 January 2010 (UTC)
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)
Special relativity ( | talk | history | protect | delete | links | watch | logs | views) has undergone an extensive rewrite over the last few days by an anonymous user (171.66.x.x; so far, 171.66.105.55 ( talk · contribs · WHOIS) and 171.66.91.179 ( talk · contribs · WHOIS), resolving to stanford.edu). These changes have been controversial. I invite all experts in the subject to review the article history and the talk page thread regarding the changes. -- Christopher Thomas ( talk) 17:20, 8 January 2010 (UTC)
Schwingers Variantionsansatz in the German Wikipedia seems to be a translation of the stub Schwinger's variational principle. The paper cited in the article (Schweber 2005) does not make any reference to a "variational principle" but to "Schwinger's quantum action principle". Thus, my question is whether the expression actually exists, or whether it is to be deleted as a newly invented expression following Wikipedia:No original research.
Our understanding is that there were several contributions (independent research of Tomonaga, Schwinger, Feynman, and Dyson) that lead to what we call perturbative Quantum Field Theory our days. Peskin/Schroeder refers to Schweber: QED and te men who made it for details. Itzykson/Zuber recover Schwinger's quantum mechanical action principle by extending the stationary phase approach to operators; however, this is meant as a description of the approach rather than an encyclopedic phrase (although admittedly appearing as "Schwinger's action principle" in their table of contents).
Imho, "Schwinger's variational principle" is a non-existing lemma. It should best be deleted. If deletion is not an option, the article should be renamed to "Schwinger's action principle", and should be placed into perspective by mentioning that it is one of several approaches to QFT. Alternatively, the text could be added to a new section "Approaches to QFT" in Quantum field theory.
A deletion/renaming of the English stub would be a good indication on how to proceed with the German page. -- Dogbert66 ( talk) 22:44, 8 January 2010 (UTC)
See Wikipedia:Featured article candidates/Speed of light/archive2. ― A._di_M. 2nd Dramaout (formerly Army1987) 17:11, 10 January 2010 (UTC)
An anon is removing a sourced section. See [1] and [2]. After my revert he left a message on the talk page. Any experts around? DVdm ( talk) 17:55, 10 January 2010 (UTC)
Could perhaps someone knowledgeable have a look at this article? I don't know anything of it but came there from Peer review where an editor User:Bourdillona was inserting self-published material. He seems to have an agenda in crystallography and has seeding several articles with links to his web sites. To be frank, he sounds like a fringe scientist to me, but that doesn't necessarily mean that he is one and his additions are perhaps legitimate. I have no way of knowing and therefore it would be helpful if someone who knows more about this stuff would have a look. Thanks. -- Crusio ( talk) 15:00, 9 January 2010 (UTC)
Sorry. The deletion was inadvertent when I wrote to an old version my mistake.
The secondary source is given: "Nearly free electron bands..." The web pages are subsidiary and the references were deleted. My profile is on Wikipedia. The 'added part' has been on wikipedia for over a year with some discussion and agreement. More debate is needed. —Preceding unsigned comment added by Bourdillona ( talk • contribs) 14:49, 11 January 2010
A little cross-wiki-project posting here. I have opened a peer review for the Combustor article over a WP:Aviation. It's a reasonably technical topic, and I'm hoping to get comments from several different groups of editors so that I get a decent feel for how easy the article is to read/understand. Please take a look at the article and leave any comments you may have at the peer review page. Thanks! - SidewinderX ( talk) 20:43, 12 January 2010 (UTC)
Wikipedia:Help desk#External Links 2 and User talk:Amanda.nelson12#January 2010 discusses external links to a large online resource of interviews with physicists and some other scientists. PrimeHunter ( talk) 17:16, 15 January 2010 (UTC)
Hi all. Could someone please take a look at the "Funding crisis" section of the Science and Technology Facilities Council article? It appears to be very misleading, particularly the subsection about Jodrell Bank. For a more accurate description, see Jodrell Bank Observatory#Threat of closure and E-MERLIN#STFC.27s Programmatic Review 2007-8. The section also needs updating to describe the latest rounds of cuts; see the STFC-provided information and Paul Crowther's summary from an astronomer POV. Some sort of a balance between the two is needed here, I guess
I have a conflict of interest here - I work at Jodrell Bank, and some of these cuts have directly affected me - so I don't feel that I can directly edit the article. I would also really struggle to maintain a neutral point of view here. However, the section of the STFC article seriously needs looking at IMO, hence my appeal here. Thanks. Mike Peel ( talk) 15:02, 16 January 2010 (UTC)
I've been doing a bit of cleanup at Talk:Quasar (added auto-archiving of very-old threads, added datestamps, split off new comments on old topics). One item I don't feel comfortable unilaterally addressing is whether or not the article is overly-technical (per the template on the talk page, which might or might not be obsolete). If you have a few idle minutes, please take a moment to glance at Quasar ( | talk | history | protect | delete | links | watch | logs | views), and to comment in the thread in question. -- Christopher Thomas ( talk) 08:26, 13 January 2010 (UTC)
Every so often, a high-traffic thread starts at Talk:Black hole about whether there's any direct evidence for black holes, and how strong or weak the circumstantial argument for them is. This time around, we have an editor making changes to the article itself, in addition to posting to the talk page thread. More eyes from experts in the field would be helpful; the relevant thread is at Talk:Black hole#Disclaimer in the Lead. The article is back at its previous consensus-state for now, but the discussion is far from over, so contributions from actual astronomers and astrophysicists would help. If nothing else, the fact that it keeps coming up on the talk page suggests that it could be clarified in the article (the last such discussion resulted in the "observational evidence" section being fleshed out). -- Christopher Thomas ( talk) 08:33, 17 January 2010 (UTC)
As this nebulium is more a spectroscopy discovery a look by a person with more knowledge in physics might be good. The article will be on the Mainpage in one hour. Thanks from the WPElements-- Stone ( talk)
This message is being sent to each WikiProject that participates in the WP 1.0 assessment system. On Saturday, January 23, 2010, the WP 1.0 bot will be upgraded. Your project does not need to take any action, but the appearance of your project's summary table will change. The upgrade will make many new, optional features available to all WikiProjects. Additional information is available at the WP 1.0 project homepage. — Carl ( CBM · talk) 03:46, 22 January 2010 (UTC)
I have a problem with the explanation found in the second paragraph of the first section:
A large object, such as a planet or star, will usually be approximately round, because large mountains will be squashed down, and large valleys filled in, by the object's own gravity.
It just seems flat out wrong. Can someone who actually understands what is trying to be said here correct the passage? -- Izno ( talk) 22:51, 10 January 2010 (UTC)
Biocentrism in cosmology has been nominated for renaming
76.66.192.206 ( talk) 05:58, 24 January 2010 (UTC)
Just created this. Extremely stub-like and in need of expansion (and attention from experts, especially for the descriptions). Headbomb { ταλκ κοντριβς – WP Physics} 18:18, 25 January 2010 (UTC)
This is a well-known series of books by Russian physicists Lev Landau and Evgeny Lifshitz. I've detailed the English publication history, but it would be nice to have the Russian side of the story. Thanks. Headbomb { ταλκ κοντριβς – WP Physics} 04:10, 28 January 2010 (UTC)
The article Second seems to imply that the definition is supposed to apply to classical free space, not quantum vacuum, so that one has to correct the measurements for the Lamb shift. This sounds weird to me; I would have assumed that it applied to quantum vacuum, i.e. space without particles or photons. Can anyone who knows better shed light on Talk:Second#Classical or quantum vacuum?? ― A._di_M. 2nd Dramaout (formerly Army1987) 11:44, 29 January 2010 (UTC)
I have all but finished this article on the new discovery by the Galaxy Zoo citizen scientists of Pea galaxies. These are some of the most star-forming galaxies in the local Universe, having rates over 1000 times faster than the Milky Way. There has been a link to the this Wiki Physics section on my discussion page, but I have only just plucked up the courage to put it here, as I am not a physicist.
If someone could rate the article- it has all the citations and has been edited thoroughly, so is waiting for a larger audience! http://en.wikipedia.org/wiki/Pea_galaxy
Thanks, Richard Richard Nowell ( talk) 10:50, 30 January 2010 (UTC)
There is currently a lot of concern across Wikipedia about how biographies of living people (BLPs) are handled (see discussion). One solution which is being considered is mass deletion of all unreferenced BLPs. While I doubt there are many significant problems in BLPs of interest to the Physics project, to avoid having our articles caught up in the process it would be worthwhile to go through them and try to get them up to the required standard. (I also suspect that getting rid of unreferenced biographies isn't going to help much in solving the real problem of people slipping contentious content about living people into various Wikipedia articles, but that viewpoint seems to be on the loosing side in the discussion!)
Based on the latest bot-generated cleanup listings, I've made a list of the articles which are tagged with WikiProject Physics BPH and also tagged as unreferenced BLPs. I'm going to try to work through the list to check whether articles are really unsourced, whether sources can be found, etc. Any help would be appreciated! Djr32 ( talk) 12:38, 31 January 2010 (UTC)
![]() | This page is an archive of past discussions. 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. |
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)
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)
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)
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)
Amidst the usual cruft, someone posted a very interesting question (at Talk:Big Bang#Underlying Assumptions). The question is about what the exact domain of applicability was of the proof that an expanding universe must have expanded from a singularity. This is way out of my league to address, but I seem to recall that there were at least a couple of GR specialists among the WP:PHYS crew. -- Christopher Thomas ( talk) 04:03, 6 January 2010 (UTC)
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)
Special relativity ( | talk | history | protect | delete | links | watch | logs | views) has undergone an extensive rewrite over the last few days by an anonymous user (171.66.x.x; so far, 171.66.105.55 ( talk · contribs · WHOIS) and 171.66.91.179 ( talk · contribs · WHOIS), resolving to stanford.edu). These changes have been controversial. I invite all experts in the subject to review the article history and the talk page thread regarding the changes. -- Christopher Thomas ( talk) 17:20, 8 January 2010 (UTC)
Schwingers Variantionsansatz in the German Wikipedia seems to be a translation of the stub Schwinger's variational principle. The paper cited in the article (Schweber 2005) does not make any reference to a "variational principle" but to "Schwinger's quantum action principle". Thus, my question is whether the expression actually exists, or whether it is to be deleted as a newly invented expression following Wikipedia:No original research.
Our understanding is that there were several contributions (independent research of Tomonaga, Schwinger, Feynman, and Dyson) that lead to what we call perturbative Quantum Field Theory our days. Peskin/Schroeder refers to Schweber: QED and te men who made it for details. Itzykson/Zuber recover Schwinger's quantum mechanical action principle by extending the stationary phase approach to operators; however, this is meant as a description of the approach rather than an encyclopedic phrase (although admittedly appearing as "Schwinger's action principle" in their table of contents).
Imho, "Schwinger's variational principle" is a non-existing lemma. It should best be deleted. If deletion is not an option, the article should be renamed to "Schwinger's action principle", and should be placed into perspective by mentioning that it is one of several approaches to QFT. Alternatively, the text could be added to a new section "Approaches to QFT" in Quantum field theory.
A deletion/renaming of the English stub would be a good indication on how to proceed with the German page. -- Dogbert66 ( talk) 22:44, 8 January 2010 (UTC)
See Wikipedia:Featured article candidates/Speed of light/archive2. ― A._di_M. 2nd Dramaout (formerly Army1987) 17:11, 10 January 2010 (UTC)
An anon is removing a sourced section. See [1] and [2]. After my revert he left a message on the talk page. Any experts around? DVdm ( talk) 17:55, 10 January 2010 (UTC)
Could perhaps someone knowledgeable have a look at this article? I don't know anything of it but came there from Peer review where an editor User:Bourdillona was inserting self-published material. He seems to have an agenda in crystallography and has seeding several articles with links to his web sites. To be frank, he sounds like a fringe scientist to me, but that doesn't necessarily mean that he is one and his additions are perhaps legitimate. I have no way of knowing and therefore it would be helpful if someone who knows more about this stuff would have a look. Thanks. -- Crusio ( talk) 15:00, 9 January 2010 (UTC)
Sorry. The deletion was inadvertent when I wrote to an old version my mistake.
The secondary source is given: "Nearly free electron bands..." The web pages are subsidiary and the references were deleted. My profile is on Wikipedia. The 'added part' has been on wikipedia for over a year with some discussion and agreement. More debate is needed. —Preceding unsigned comment added by Bourdillona ( talk • contribs) 14:49, 11 January 2010
A little cross-wiki-project posting here. I have opened a peer review for the Combustor article over a WP:Aviation. It's a reasonably technical topic, and I'm hoping to get comments from several different groups of editors so that I get a decent feel for how easy the article is to read/understand. Please take a look at the article and leave any comments you may have at the peer review page. Thanks! - SidewinderX ( talk) 20:43, 12 January 2010 (UTC)
Wikipedia:Help desk#External Links 2 and User talk:Amanda.nelson12#January 2010 discusses external links to a large online resource of interviews with physicists and some other scientists. PrimeHunter ( talk) 17:16, 15 January 2010 (UTC)
Hi all. Could someone please take a look at the "Funding crisis" section of the Science and Technology Facilities Council article? It appears to be very misleading, particularly the subsection about Jodrell Bank. For a more accurate description, see Jodrell Bank Observatory#Threat of closure and E-MERLIN#STFC.27s Programmatic Review 2007-8. The section also needs updating to describe the latest rounds of cuts; see the STFC-provided information and Paul Crowther's summary from an astronomer POV. Some sort of a balance between the two is needed here, I guess
I have a conflict of interest here - I work at Jodrell Bank, and some of these cuts have directly affected me - so I don't feel that I can directly edit the article. I would also really struggle to maintain a neutral point of view here. However, the section of the STFC article seriously needs looking at IMO, hence my appeal here. Thanks. Mike Peel ( talk) 15:02, 16 January 2010 (UTC)
I've been doing a bit of cleanup at Talk:Quasar (added auto-archiving of very-old threads, added datestamps, split off new comments on old topics). One item I don't feel comfortable unilaterally addressing is whether or not the article is overly-technical (per the template on the talk page, which might or might not be obsolete). If you have a few idle minutes, please take a moment to glance at Quasar ( | talk | history | protect | delete | links | watch | logs | views), and to comment in the thread in question. -- Christopher Thomas ( talk) 08:26, 13 January 2010 (UTC)
Every so often, a high-traffic thread starts at Talk:Black hole about whether there's any direct evidence for black holes, and how strong or weak the circumstantial argument for them is. This time around, we have an editor making changes to the article itself, in addition to posting to the talk page thread. More eyes from experts in the field would be helpful; the relevant thread is at Talk:Black hole#Disclaimer in the Lead. The article is back at its previous consensus-state for now, but the discussion is far from over, so contributions from actual astronomers and astrophysicists would help. If nothing else, the fact that it keeps coming up on the talk page suggests that it could be clarified in the article (the last such discussion resulted in the "observational evidence" section being fleshed out). -- Christopher Thomas ( talk) 08:33, 17 January 2010 (UTC)
As this nebulium is more a spectroscopy discovery a look by a person with more knowledge in physics might be good. The article will be on the Mainpage in one hour. Thanks from the WPElements-- Stone ( talk)
This message is being sent to each WikiProject that participates in the WP 1.0 assessment system. On Saturday, January 23, 2010, the WP 1.0 bot will be upgraded. Your project does not need to take any action, but the appearance of your project's summary table will change. The upgrade will make many new, optional features available to all WikiProjects. Additional information is available at the WP 1.0 project homepage. — Carl ( CBM · talk) 03:46, 22 January 2010 (UTC)
I have a problem with the explanation found in the second paragraph of the first section:
A large object, such as a planet or star, will usually be approximately round, because large mountains will be squashed down, and large valleys filled in, by the object's own gravity.
It just seems flat out wrong. Can someone who actually understands what is trying to be said here correct the passage? -- Izno ( talk) 22:51, 10 January 2010 (UTC)
Biocentrism in cosmology has been nominated for renaming
76.66.192.206 ( talk) 05:58, 24 January 2010 (UTC)
Just created this. Extremely stub-like and in need of expansion (and attention from experts, especially for the descriptions). Headbomb { ταλκ κοντριβς – WP Physics} 18:18, 25 January 2010 (UTC)
This is a well-known series of books by Russian physicists Lev Landau and Evgeny Lifshitz. I've detailed the English publication history, but it would be nice to have the Russian side of the story. Thanks. Headbomb { ταλκ κοντριβς – WP Physics} 04:10, 28 January 2010 (UTC)
The article Second seems to imply that the definition is supposed to apply to classical free space, not quantum vacuum, so that one has to correct the measurements for the Lamb shift. This sounds weird to me; I would have assumed that it applied to quantum vacuum, i.e. space without particles or photons. Can anyone who knows better shed light on Talk:Second#Classical or quantum vacuum?? ― A._di_M. 2nd Dramaout (formerly Army1987) 11:44, 29 January 2010 (UTC)
I have all but finished this article on the new discovery by the Galaxy Zoo citizen scientists of Pea galaxies. These are some of the most star-forming galaxies in the local Universe, having rates over 1000 times faster than the Milky Way. There has been a link to the this Wiki Physics section on my discussion page, but I have only just plucked up the courage to put it here, as I am not a physicist.
If someone could rate the article- it has all the citations and has been edited thoroughly, so is waiting for a larger audience! http://en.wikipedia.org/wiki/Pea_galaxy
Thanks, Richard Richard Nowell ( talk) 10:50, 30 January 2010 (UTC)
There is currently a lot of concern across Wikipedia about how biographies of living people (BLPs) are handled (see discussion). One solution which is being considered is mass deletion of all unreferenced BLPs. While I doubt there are many significant problems in BLPs of interest to the Physics project, to avoid having our articles caught up in the process it would be worthwhile to go through them and try to get them up to the required standard. (I also suspect that getting rid of unreferenced biographies isn't going to help much in solving the real problem of people slipping contentious content about living people into various Wikipedia articles, but that viewpoint seems to be on the loosing side in the discussion!)
Based on the latest bot-generated cleanup listings, I've made a list of the articles which are tagged with WikiProject Physics BPH and also tagged as unreferenced BLPs. I'm going to try to work through the list to check whether articles are really unsourced, whether sources can be found, etc. Any help would be appreciated! Djr32 ( talk) 12:38, 31 January 2010 (UTC)