User talk:Sbyrnes321

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[edit] Welcome to Wikipedia!!!

Hello Sbyrnes321! Welcome to Wikipedia! Thank you for your contributions. If you decide that you need help, check out Wikipedia:Where to ask a question, ask me on my talk page, or place {{helpme}} on your talk page and someone will show up shortly to answer your questions. Please remember to sign your name on talk pages using four tildes (~~~~); this will automatically produce your name and the date. You may also push the signature button located above the edit window. Finally, please do your best to always fill in the edit summary field. This is considered an important guideline in Wikipedia. Even a short summary is better than no summary. Below are some recommended guidelines to facilitate your involvement. Happy editing! -- Kukini 00:03, 12 December 2006 (UTC) Getting Started Wikipedia Tutorial How to edit a page The five pillars of Wikipedia Manual of Style Be bold in editing How to write a great article WikiProjects Getting your info out there Cite your sources Neutral Point of View Point of View Verifiability Uploading images Image use policy Getting more Wikipedia rules Policy Library Getting Help New contributors' help page Where to ask a question Help Desk Frequently Asked Questions Getting along Wikiquette Civility Sign your posts Wikipedians Conflict resolution Getting technical Cleaning up vandalism Pages needing attention Peer review Utilities Village pump

[edit] Kevins Note

Hi.

Your rewrite is much better, but I think it still don’t address some issues. I can’t say that I agree that the product of statistical standard deviations imply anything about the measurement of an individual event. To actually calculate a standard deviation, say of x, one needs to have a measurement error much less than the standard deviation for the calculation to make sense. Measurement error, δp and δq, is not the same as standard deviations, and in fact can not be related.

e.g. http://plato.stanford.edu/entries/qt-uncertainty/#2.3,

to wit:

• quote

“A solution to this problem can again be found in the Chicago Lectures. Heisenberg admits that position and momentum can be known exactly. He writes:

"If the velocity of the electron is at first known, and the position then exactly measured, the position of the electron for times previous to the position measurement may be calculated. For these past times, δpδq is smaller than the usual bound. (Heisenberg 1930, p. 15)

Indeed, Heisenberg says: "the uncertainty relation does not hold for the past". “ etc…

And, according to Ballentine, deltaQ and deltaP are not even calculated at the some instant in time. I’ll just paste some stuff in, and see what you think

1Ballentine "Quantum Mechanics, A Modern development" P.225- P.226 (reference to graphs of delta_x and error_x, showing them not the same)

"...One must have a repeatable preparation procedure corresponding to the state p which is to be studied. Then on each one of a large number of similarly prepared systems, one performs a single measurement (either Q or P). The statistical distributions of the results are shown as histograms, and the root mean square half-widths or the two distributions deltaQ and deltaP, are indicated in fig. 8.2. The theory predicts that the product of these two half-widths can never be less then hbar/2, no matter what state is considered."

"To the reader who is unfamiliar with the history of quantum mechanics, these remarks may seem to belabor the obvious. Unfortunately the statistical quantities delta_q and delta_p in(8.33) have often been misinterpreted as the errors of individual measurements. The origin of the confusion probably lies in the fact that Heisenberg's original paper on the certainty principle, published in 1927, was based on early work that predates the systematic formulation and statistical interpretation of quantum theory. Thus the natural derivation and interpretation of (8.33) that is given above was not possible at the time. The statistical interpretation of the indeterminacy relations was first advanced by K.R. Popper in 1934." (8.33) - delta_x.delta_p >=1/2|<C>|, the result hold for any operators that satisfy [A,B]=iC"

2Ballentine "Quantum Mechanics, A Modern development" P. 225-226

"Jauch (1993). The rms atomic momentum fluctuation, delta_p is directly obtained from the temperature of the crystal, and hence gives a lower bound to delta_q, the rms vibration amplitude of an atom. The value of delta_x can be measured by neutron diffraction, and at low temperature it is only slightly above its quantum lower bound, hbar/2delta_p. Jauch stresses that it is only the rms ensemble fluctuations that are limited by (8.33). The position coordinates of the atomic cell can be determined with a precision that is two orders of magnitude smaller then the quantum limit on delta_q".

Jauch (1993) - Heisenberg's Uncertainty Relation and Thermal Vibrations in Crystals, Am. J. Phys. 61, 929-932 —Preceding unsigned comment added by Kevin aylward (talk • contribs) 13:48, 15 September 2007 (UTC)

Thanks for the message! If I'm reading right, I absolutely agree with that, and in fact your quote from Ballentine conveys precisely the same message as the section on the observer effect. (And as Ballentine says, Heisenberg himself didn't understand the HUP in the same way modern physicists do.) The standard-deviation-not-measurement error issue is certainly a worthwhile nuance to get straight (hence the whole "observer effect" section), and if you find anywhere that confuses the issue, or anywhere where it could be explained better, I hope you go ahead and do that. Or tell me and I'll do it. --Steve 23:09, 15 September 2007 (UTC)

[edit] Measurement in quantum mechanics

hello. i noticed you were cleaning up that article, which was degenerating into something not good. thanks. hope you don't mind me making couple suggestions. the article still contains some funny statements. in particular, some statements referring to the mathematical formulation doesn't quite make sense. perhaps better to rewrite the whole thing in physicist's language without the pretense of rigor. also, seems to me couple sections of the article could be removed in their entirety. thanks again and hope to see you around. Mct mht 02:44, 23 October 2007 (UTC)

Thanks for the message! Unfortunately I'm not at all knowledgable regarding interpretations of quantum mechanics, and only a little knowledgable about decoherence. So I'm unlikely to edit anything after the (current) first section. If the rest of the article is to be fixed up (and it should), it won't be my doing. Feel free to do it yourself though!

I deleted one full section. I was also thinking of deleting the "example" section, but rewrote it instead. It's still potentially deleteable though, I wouldn't be offended. Since your message, there was one place (Hermitian operators not always having complete eigenbases) where I tried to brush aside some mathematical details without actually making any incorrect statements. I think that should be the goal, and if there's other places where you see opportunity to do the same, go for it. --Steve 00:56, 24 October 2007 (UTC)

Update: I revised the rest of the article, notwithstanding my lack of expertise. Could use a few more references and detail, I suppose. Also, the "von Neumann measurement scheme" is a bit unreadable, but seemingly worth keeping in...don't really know what to do with that. --Steve (talk) 07:17, 20 November 2007 (UTC)

hi again, Steve. you seem to be doing a lotta clean up. quantum state is in much improved state after the contributions of you and User: B. Wolterding. may i suggest you consider taking a look at bra ket notation? Mct mht (talk) 02:46, 27 November 2007 (UTC)

[edit] Electron is a magnet

Can you explain by what nature an 'electron is by its nature a magnet?' I think this statement under Magnetism needs to be supported or if it can't, should go. John 06:35, 13 November 2007 (UTC)

I think that "see electron magnetic dipole moment" is a reasonable enough justification in this context. The electron has a magnetic moment, it's equal to 9× 10^-24 J/T, and it's just a property of every electron in the universe. There isn't really any deeper explanation. I guess you could say it has a magnetic moment because it has a nonzero spin, but why does it have a nonzero spin? Because that's the way it works out in the standard model. In any case, having a magnetic moment is undoubtedly and uncontroversially part of the "nature" of an electron. If you think a reference is called for, any book on quantum mechanics will do.

By the way, despite the name "spin", the electron is not literally rotating about an axis. A much better explanation is that it's just an intrinsic property of the electron. Again, any quantum-mechanics book written since 1950 will tell you that. --Steve 18:00, 13 November 2007 (UTC)

Then could it state that it has a magnetic property because of the quantum mechanical spin property? I think this needs something for laymen assessability. John 19:04, 13 November 2007 (UTC)

Hmm...Well no one would think twice about saying that the reason an electron has a charge of -1.6*10^-19 Coulombs is that "it just does" or "it's a property of the electron". Nor would anyone require a deeper explanation of the fact that the electron's mass is 10^-30 kg. I'm proposing that we say something analogous regarding the electron's magnetic moment. Why should that be any different?

My view is that bringing up spin in this context doesn't add any illumination. A lay reader can be prodded to accept that an electron has a certain magnetic moment just like it has a certain electric charge, just because that's what an electron is. But saying that it has a magnetic moment because of something called spin doesn't help matters at all: First, the reader needs to look up the article spin; second, the reader won't understand how the spin gives rise to a magnetic moment (and won't understand it without QED), and third, the reader will wonder...why does the electron have spin? And the answer is: Just because that's what an electron is. (So you're still stuck with an unjustified assertion about the nature of the electron, only this time it's one which is harder to understand.) --Steve 21:43, 13 November 2007 (UTC)

I claim magnetism is different because it is not a fundamental property, is a derrived property, charge, mass and (maybe) spin aren't; ...and magnetism is what this article is about, after all. To cite that a derrived property 'just is' is a little misleading in that it implies the representation that it is a fundamental property. If we don't know what it is derrived from, then lets admit it. Would an electron with no spin have a magnetic moment? To answer that in the negative implies a pair of monopoles in it. I think we should call a spade a spade here. John 20:54, 14 November 2007 (UTC)

Mass is widely accepted to be a derived property, a consequence of the Higgs mechanism. But the article mass, for good reason, doesn't mention this bit of quantum field theory. Charge is also a derived property, derived from the more fundamental electroweak theory. Moreover, according to string theory (for example), my understanding is that the electron itself is a derived particle, coming from more fundamental interactions with strings and vaccuums.

I guess what I'm saying is, there's different levels of explanation. A biology article can say a metabolic pathway functions because these two chemicals react. A chemistry article can say two chemicals react because of electron orbital interactions. A general physics article can say electrons have orbitals because of the Pauli exclusion principle. An article on the Pauli exclusion principle can talk about the spin-statistics theorem derived from quantum field theory. And so on, and so on. The purpose of this particular paragraph is explaining magnetism in materials, and the most important cause of this is that electrons have magnetic moments. Readers interested in the more fundamental question of why electrons have magnetic moments are explicitly redirected to the article electron magnetic dipole moment, where they can learn lots about it. The article doesn't imply that there's no deeper explanation of the dipole moment; on the contrary, it makes it very easy to find that explanation. I think that should be the goal.

By the way, an electron with no spin isn't an electron. An electron which didn't interact with photons wouldn't have charge, and that wouldn't be an electron either. --Steve 23:01, 14 November 2007 (UTC)

[edit] Vector (spatial)

Hi Steve, this is one of those articles that gets a lot of little edits by hacks (like me) and ends up getting fragmented. Articles like this need periodic copyedits or rewrites. I saw your note on the talk page - go for it - be bold - the article could use some TLC. --Duk 20:33, 30 November 2007 (UTC)

Thanks for the encouragement :-) Happy holidays! --Steve 20:42, 30 November 2007 (UTC)

[edit] Tension Myositis Syndrome

Hi, Steve. Thanks for your enthusiasm and willingness to help out with the TMS article. Unfortunately, I will need to rework much of what you wrote in the Notable Patients section. TMS is highly controversial and the article was on the AFD (article for deletion) list in September. The article came close to being deleted. Two of the main complaints about the article at that time were (a) the use of self-published sources (most notably Sarno's books) and (b) lack of neutrality. I think that some of your changes in the Notable Patients section tend to reintroduce some of those problems back into the article. I will try to salvage what I can of what you've written.

So far, I've only made one change. I restored my wording about John Stossel, with a brief summary of the reasons in the edit comment. Feel free to ask for a more detailed description if you like. -- JTSchreiber (talk) 06:05, 23 December 2007 (UTC)

Thanks for the note! That's a sound change, and I'm glad you're keeping me honest :-). I don't suspect you'll find many source problems in this section, but there may be NPOV problems, like the one you pointed out. On the other hand, if some celebrity thinks that Sarno is the best thing since penicillin, it would be wrong (a misuse of NPOV) for the article not to convey that opinion. In other words, the way in which a celebrity views their own treatment is in itself notable, and should be included, but with it made clear that that's their opinion (and not a rock-hard fact about their medical history). Even so, there may be NPOV issues, so by all means take a look. By the way, I'll be sure to eventually copy your changes to the identical section in John E. Sarno. Happy holidays! --Steve (talk) 06:36, 23 December 2007 (UTC)

You're welcome for the note. I think that the most important source problem is the use of the back cover of Sarno's book. The statements on a book's cover are basically advertising for the book, and those statements haven't necessarily gone through the type of fact-checking process used by major newspapers, etc.

"[I]f some celebrity thinks that Sarno is the best thing since penicillin, it would be wrong (a misuse of NPOV) for the article not to convey that opinion. " Yes and no. Part of the problem is that all of the article's notable patients have glowing things to say about Sarno and his TMS treatment, so the impression is not balanced. If we added a quote from one notable patient who had been through TMS treatient and hated it, then the section would be more neutral. If we can't find such a quote, printed in a reliable source, then I think the only alternative is to paraphrase the enthusiastic patients' comments in a less enthusiastic way. Happy Holidays! --JTSchreiber (talk) 06:04, 24 December 2007 (UTC)

Hi again! My view was that a bestselling book by a reputable publisher was unlikely to go out with fabricated quotes on the cover, especially when other sources lend plausibility. Nevertheless, I can switch out the Howard Stern quote for something from his book (which we know he wrote), and I'll look a bit more for Anne Bancroft quotes. A compromise for the latter case might be to say "She was quoted by Sarno as saying..." and let the reader judge whether that's a reliable source.

The way I see it is, all the celebrities who say publicly that they've been treated by Sarno have very enthusiastic things to say. If that's the way it is in real life, that's the way it ought to be portrayed in an encyclopedia article. As far as I can tell, there aren't any celebrities who were treated by Sarno and publicly said they hated it...if any are found, of course they should go in the section, but the lack of such celebrities shouldn't have any bearing on the fidelity with which the other celebrities' experiences are portrayed, right? I dunno, maybe I'm not thinking straight because I'm biased, I'll think more about it. Happy holidays once again! --Steve (talk) 14:47, 24 December 2007 (UTC)

"[A] bestselling book by a reputable publisher was unlikely to go out with fabricated quotes on the cover." This got me thinking. I checked the TMS article's AFD discussion and some Wikipedia policies. I must have picked up an incorrect definition of self-published from an editor who had wanted the TMS article deleted. On Wikipedia, "self-published" means released by a vanity press, so Sarno's books do not qualify. Instead, his books are from reliable publishers, providing a reliable source for the quotes.

"the lack of such celebrities shouldn't have any bearing on the fidelity with which the other celebrities' experiences are portrayed, right?" I don't think so. The NPOV policy says that, "A common type of dispute is when an editor asserts that a fact is both verifiable and cited, and should therefore be included... Concerns related to undue weight, non-neutral fact selection and wording, and advancing a personal view, are not addressed even slightly by asserting that the matter is verifiable and cited."

I think it's helpful to look at other notable patient sections as examples. I did a Google search of Wikipedia for "Notable patients" and looked at all the articles found. The followihg three articles are good examples: Non-Hodgkin lymphoma, Lupus erythematosus and Mesothelioma. All of them are rated B-class, a higher level than the TMS article. The notable patient sections in these three articles all come across as much more neutral than the TMS article. I still intend to edit the TMS notable patients section to be more neutral. Happy Holidays! --JTSchreiber (talk) 06:16, 27 December 2007 (UTC)

Another example: I'd be a little disconcerted if Scientology had long quotes from Tom Cruise about how it's improved his life :-) Reading it again, I was thinking the problem might be alleviated a bit by altering the wording to further distance the celebrity quotes from the narrative of the article, so I did that. But go ahead and edit it further when you get a chance. Still enjoying this illuminating conversation, --Steve (talk) 05:44, 28 December 2007 (UTC)

Yes, I thought of the Cruise example myself. I've reworked the notable patient section of John E. Sarno to be more neutral. I achieved neutrality (I hope) by balancing the glowing comments of the patients with the somewhat sarcastic Newsweek comment. My rework was also intended to make that section distinct from the TMS notable patient section. I think it's important to keep these distinct, because during the AFD discussion of the TMS article, some had suggested merging the TMS article into the Sarno article. I think that would be a shame, so I'd like to keep the two articles as distinct as possible. --JTSchreiber (talk) 05:02, 29 December 2007 (UTC)

Well I approve. Good going, and sorry to make more work for you. Best, Steve (talk) 23:16, 29 December 2007 (UTC)

Thanks for the approval. This discussion was a good chance for me to learn more about Wikipdia policies. Have a happy New Year! --JTSchreiber (talk) 04:29, 30 December 2007 (UTC)

Hello, again. I had a question about your latest addition to the TMS article. Was the reference to Stern's Miss America book supposed to cover both pain and OCD? The current wording for pain is a quote from the back cover of the Sarno book, so the Stern book can't really be used as a source for that. Is it OK to use the Stern book reference just for OCD? --JTSchreiber (talk) 05:55, 3 January 2008 (UTC)

It's like a 30-page book chapter where he talks about everything -- coming down with OCD, back pain, his appointment with Sarno, etc. Ideally, the back cover would be a source for the quote, and Miss America would be a source for the whole sentence. Perhaps the back-cover reference could be moved to immediately after the quote, and Miss America could be left after the period? --Steve (talk) 16:03, 3 January 2008 (UTC)

OK, I adjusted the referencing of the Stern sentence. Since Stern has a whole chapter on his back pain and OCD in Miss America, does he have a noteworthy quote for the John E. Sarno article? The quote would have to be brief. --JTSchreiber (talk) 05:47, 4 January 2008 (UTC)

Unfortunately, I no longer have access to the book (I was visiting relatives last week, who had the book). I did read the chapter, because I was curious, but didn't write down any quotes or excerpts. Maybe I'll find one next time I visit, whenever that is. Or someone else with the book will think to add a quote. In the meantime, wikipedia will have to do without. Sorry! :-) --Steve (talk) 16:14, 4 January 2008 (UTC)

[edit] Theory of Everything

Thanks for referencing and sourcing the argument you called "Non NPOV OR". I wrote it, and it's much better now.Likebox (talk) 07:11, 31 December 2007 (UTC)

You're welcome. No offense intended :-) Happy new years!! --Steve (talk) 00:38, 1 January 2008 (UTC)

[edit] Magnetic monopoles

It would be a good idea to have both cgs and SI equations in the article. --161.53.6.108 (talk) 16:29, 16 January 2008 (UTC)

[edit] questions

hi, Steve. i was asked some physics questions: User talk:Mct mht#Part III: Question. could you perhaps consider taking a stab at it? Mct mht (talk) 19:51, 26 January 2008 (UTC)

[edit] Migraine

[edit] Denuelle study

Your Revision of 00:45, 7 February 2008 removes my paragraph. You state "This is one of thousands of migraine studies, and doesn't stand out as worthy of inclusion. Also, text is plagiarized".

While not disputing that there have been thousands of migraine studies, I wonder could you refer me to one other where PET was used for patients with naturally occurring episodes or to one other which implicates the hypothalamus so directly? Or for that matter, where PET or the hypothalamus are mentioned elsewhere in this article?

You accuse me of plagiarism. If by this you mean that I have taken the facts reported in the BBC article and re-written them in my own summary, using some of the same words, that may be true. But I rather resent being accused of stealing ideas. After all the facts are the facts, aren't they? I thought that was what wiki editing was all about.

I do not have access to the journal "Headache" (to which I provided a direct web link for anyone interested) and only have this BBC report to go on. If your issue is with really with "plagiarism" then I would urge you to read the original journal article yourself and to re-write it in YOUR own words.

You are obviously an able and industrious wikipedian and I do not dispute the quality of your edits. I cannot claim to be a migraine expert. But I do resent having my edit, made in good faith, summarily thrown away quite so expertly. I'm sure we don't want an article where all the interesting or topical facts have been very carfefully "tidied away". I honestly judged that the Denuelle study was a small breakthrough and of genuine interest to students and sufferers alike. Martinevans123 (talk) 21:13, 7 February 2008 (UTC)

Hello! Thanks for drawing my attention to your comment, by posting it here. I responded on the migraine talk page. --Steve (talk)

Thank you for your apologies which are fully accepted. Your reasoning is perfectly valid and I agree with you. Perhaps we could compromise on a single short sentence? I realise that there is a trade-off between topicality and balance in such articles as this - I supppose what I'm reeally looking for is a "news" subsection that could be edited on a weekly/ monthly basis. Thanks, anyway. My aplogies for dumping this on your talk page - please delete if you wish. Martinevans123 (talk) 10:53, 8 February 2008 (UTC)

I'm happy with your current phrasing.--Steve (talk) 17:46, 15 February 2008 (UTC)

cool Martinevans123 (talk) 22:05, 15 February 2008 (UTC)

[edit] Talk about it

Template talk: Quantum mechanics2. I responded to you there. Please talkback. ScienceApologist (talk) 16:08, 11 February 2008 (UTC)

[edit] Lorentz Force

I like the changes you have made to the article - much improved. Thanks! PhySusie (talk) 17:18, 21 February 2008 (UTC)

[edit] Ampere's laws

I made a new article out of the "force law" and tried to link to all suitable articles. Because of its importance to SI units, I think this approach provides better emphasis than a sub-heading in an article that doesn't even have Ampere in its title. As a minor plus, it also makes it more evident why "circuital" is used in describing "Ampere's circuital law". Brews ohare (talk) 22:01, 21 February 2008 (UTC)

Fine with me! :-) --Steve (talk) 23:39, 21 February 2008 (UTC)

[edit] Free space = empty space??

The article presently says:

The notion of free space does not correspond to the present-day understanding of what is called the vacuum state or the quantum vacuum, which is "by no means a simple empty space".^[1], and again: "it is a mistake to think of any physical vacuum as some absolutely empty void."^[2] According to quantum mechanics, empty space (the "vacuum") is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence.^[3]

I took these references as support for the view that the "customary" view of free space was that it was what you call bare vacuum. Maybe instead "free space" should be defined as the physical vacuum occurring in nature? Then how are these quotations to be interpreted? See Talk:Free_space for more. Brews ohare (talk) 21:22, 1 March 2008 (UTC)

Here is an even clearer usage of vacuum in common parlance: In classical physics this principle [relativity] applies to motion in vacuum, which is just another name for empty space. But the face of the problem today is changed by quantum theory. Quantum vacuum is no longer empty.^[4] Brews ohare (talk) 22:03, 1 March 2008 (UTC)

And here is a whole book about it. ^[5] Brews ohare (talk) 22:15, 1 March 2008 (UTC)

1. ^ Astrid Lambrecht (Hartmut Figger, Dieter Meschede, Claus Zimmermann Eds.) (2002). Observing mechanical dissipation in the quantum vacuum: an experimental challenge; in Laser physics at the limits. Berlin/New York: Springer, p. 197. ISBN 3540424180. 
2. ^ Christopher Ray (1991). Time, space and philosophy. London/New York: Routledge, Chapter 10, p. 205. ISBN 0415032210. 
3. ^ AIP Physics News Update,1996
4. ^ Relativity of motion in quantum vacuum
5. ^ Henning Genz (2002). Nothingness: the science of empty space. Reading MA: Oxford: Perseus. ISBN 0738206105. 

[edit] Further developments

It would be helpful if you would comment on the free space article. Brews ohare (talk) 17:35, 2 March 2008 (UTC)

I know, I will as soon as I get a chance. It seems that Wikipedia isn't the only thing in my life, even if sometimes I wish it were :-) --Steve (talk) 19:03, 2 March 2008 (UTC)

[edit] Style note

Hi. Thank you for your work. And just a small comment. On Wikipedia, one should use lowercase in section names, like in this correction. Cheers, Oleg Alexandrov (talk) 03:48, 4 March 2008 (UTC)

[edit] ε₀ a scalar

Hi Steve: A question - is it a result of special relativity that the speed of light in vacuum is a scalar? What about the dichroism of vacuum predicted by QED? -That must be compatible with all the symmetry behaviors, yet suggests the vacuum can have dichroism and birefringence. Why do we believe that c₀ and μ₀ are so simple? Brews ohare (talk) 06:23, 4 March 2008 (UTC)

I'm not familiar with "dichroism of the vacuum predicted by QED", so I can't really help you too specifically :-) I mean, nothing in physics is known 100%...for example, serious physicists are constantly engaging in theoretical studies and expensive experimental searches for things like Lorentz Invariance not exactly holding, or the electron having not-quite the opposite charge of a proton, or the laws of physics being anisotropic, etc. See Lorentz covariance for an example of that in an article, albeit uncited. If a theorist has a model in which "ε₀ is not so simple", then someone else has probably done an empirical study that says "ε₀ is known to be simple to an accuracy of one part in 4.697 billion", and putting both of those facts into an article would be a fine addition, as far as I'm concerned. --Steve (talk) 17:19, 4 March 2008 (UTC)

I am reassured. Here's an example, just FYI Gies, H et al.: Polarized light propagating in a magnetic field as a probe for millicharged fermions Phys. Rev. Letts. 97 (2006) 140402. Brews ohare (talk) 18:44, 4 March 2008 (UTC)

[edit] Radiation reaction force

Hi Steve: I need some education here. I understood that to mean something like the self-energy effect. Are external forces, like Bremsstrahlung, subsumed under this effect? If so, why not include the links to Bremsstrahlung and synchrotron light just to make the point more evident? Brews ohare (talk) 18:14, 10 March 2008 (UTC)

I'm a bit unhappy with the article on radiation reaction because it (i) has no references and (ii) uses a third order derivative to get the force, which I very much doubt is valid in general. I'd expect some ħ's and p·A's to show up. Brews ohare (talk) 18:26, 10 March 2008 (UTC)

Ah, I linked to the worse of two duplicate articles. Take another look... :-) --Steve (talk) 18:33, 10 March 2008 (UTC)

Hmm, in Bremsstrahlung, the electric and magnetic fields of the electron affect the surrounding crystal, which in turn makes an electric field which opposes the motion and slows down the particle (at least, classically, I imagine that's how it has to work). Meanwhile, the fact that synchrotron radiation can be produced by, say, spinning an electron in a circle, is a neat fact, and the net result of that phenomenon is that there's a radiation reaction force on the electron. So...maybe we can say there's a direct force, namely radiation reaction which is associated with the release of radiation, such as synchrotron radiation, and an indirect force, where the fields affect the local charges and currents, such as in Bremsstralung. Does that sound sufficiently concrete and accurate? --Steve (talk) 18:55, 10 March 2008 (UTC)

I'm beyond my depth on this. I modified the article in a way that doesn't require much knowledge. You might take a look at Haug. Brews ohare (talk) 19:18, 10 March 2008 (UTC)

[edit] Abraham-Lorentz force

Steve, we edited the article Abraham-Lorentz force at the same time. Please take a look to see if you are OK with the result. Some edits may have been overwritten. Brews ohare (talk) 19:50, 14 March 2008 (UTC)

[edit] Faraday's law

Please take a look at the integral form of this law I have added, and see if it re-opens or maybe can be used to clarify all the bru-haha in this article. Brews ohare (talk) 05:54, 15 March 2008 (UTC)

Hello!! Well the diagram and notational changes are fine, but I'm skeptical about this paragraph:

The surface integral at the right-hand side of this equation is the explicit expression for the magnetic flux ΦB through Σ. If the closed contour ∂Σ varies with time, then the bounding surface Σ also becomes time dependent. In that case, the derivative with respect to time has two terms, one the time-differentiated integrand and the other related to the time-derivative of the boundary motion. In particular, if the B-field is time independent, and the curve ∂Σ moves through this stationary magnetic field, an EMF is generated in the loop ∂Σ by the time-derivative term related to boundary motion.

For example, if B is uniform and time-independent, and ∂Σ is a loop that shrinks over time, it sounds like you're implying that the loop integral of E would be nonzero due to the "boundary terms". But actually, E is zero everywhere, as is its loop integral around any loop. The fact that the EMF is nonzero is different, since the EMF here doesn't come from the loop-integral of E. Or does this come from somewhere? Hope all is well! --Steve (talk) 17:33, 15 March 2008 (UTC)

Hi Steve: Neat example. I'd say that the EMF version of Faraday's law says the same thing - a loop with shrinking area in a constant B-field will see a time varying Ф_B. Got any intuition about this one? For example, for a rectangular loop let the width of the rectangle decrease with time. Suppose the center of the loop is stationary. The left side moves to the right, and right side moves to the left. Apparently the v × B forces are opposite in the wires, so a current will flow. Do you agree? Brews ohare (talk) 20:31, 15 March 2008 (UTC)

Please also take a look at Lorentz force law which has similar changes. Brews ohare (talk) 20:36, 15 March 2008 (UTC)

Thanks for the head's up! :-) I posted some commentary at Faraday's law of induction. --Steve (talk) 23:04, 15 March 2008 (UTC)

Please take another look. Brews ohare (talk) 23:37, 16 March 2008 (UTC)

Hi Steve

Added a moving observer example at Faraday's law. Any comments? Brews ohare (talk) 03:45, 22 March 2008 (UTC)

[edit] Moving magnet and conductor problem

Moving magnet and conductor problem was a total disaster area. In particular, it confused the Lorentz law with Newton's law of motion with a Lorentz force. The section on showing the results in both frames were the same was full of irrelevancies, and had to be rewritten to make any sense. Take a look at it now, please. Brews ohare (talk) 20:19, 27 March 2008 (UTC)

Personally, I hadn't even read it. I'd be happy to take a look and offer feedback when I get a chance, but it may not be for a few days. :-) --Steve (talk) 20:24, 27 March 2008 (UTC)

Hi Steve:

Please take another look at this article and see if you agree with changes. Brews ohare (talk) 00:57, 14 April 2008 (UTC)

[edit] Inapplicability of Faraday's law

Hi Steve: I wonder if you are comfortable with Feynman's example? I'm uneasy with it. For example, suppose I choose a radial strip (a slice of pie) in the disc and follow it around the rotation. This seems to me to be another example of the moving loop in an inhomogeneous B-field, and Faraday's law works for this case. So then I just add up all the strips in the disk. Faraday's law works for each strip, so it works for the whole disc. What do you think? Brews ohare (talk) 14:25, 18 April 2008 (UTC)

The section "Using classical theory" already has a pretty good explanation, I think, of how to apply the flux rule and get the right answer (although maybe it's a bit "handwavey"). More generally, I think there are two legitimate approaches:

• (1) You say the flux rule is an always-true law, but that it has to be stated in a really complicated way in order to still be correct when the material of the circuit is changing, or
• (2) You say the flux rule is a very simple law, but that it stops being true when the material of the circuit is changing.

It's sorta like alternate ways to define and use the flux rule, and I think it's worthwhile to present both perspectives. --Steve (talk) 16:54, 18 April 2008 (UTC)

Hi Steve: Here's what I'm thinking - what's your take?

Figure 1: Feynman disc

The figure shows an example. The B-field is stationary and normal to the disc and depends on θ: say

  0 < θ < π

             π < θ < 2π

Then the currents are clockwise for wedges on the right and counterclockwise for wedges on the left. There is no current for the wedge pointed straight up ( θ = π/2 ) because the B-field is the same on both edges. There is no current in wedges in the lower half because B = 0. Adding everything up, I get zero EMF, just like Faraday's law says. Brews ohare (talk) 17:01, 18 April 2008 (UTC)

I'm confused. I thought that what Feynman did was have a *uniform* magnetic field *normal* to the disk. Am I misunderstanding your figure, or misremembering Feynman? Neither of the figures in the article is consistent with that, but the text-explanation "equipment, procedure" is. (essentially). --Steve (talk) 17:09, 18 April 2008 (UTC)

Sorry: I took the essence of the Feynman example to be the spatially localized nature of the B-field in only part of the disc. A generalization would be any inhomogeneous B-field. So instead of a rectangular step in field I took a sin(θ) dependence over only half the disc. Do you think there is an essential difference in these cases? Brews ohare (talk) 17:14, 18 April 2008 (UTC)

The phenomenon still occurs with an entirely-uniform magnetic field... --Steve (talk) 17:17, 18 April 2008 (UTC)

Roger. But is the limitation of the uniform field region to only part of the disc important? I'll do some more thinking here. It looks like having a uniform field over the whole disc will result in driving charge to the rim which has to taken away by the brush. So the Fynman thing still works - Faraday's law is a bust. The figure in the paradox article should be changed to this case. Brews ohare (talk) 17:34, 18 April 2008 (UTC)

Figure 2: Faraday Disc

Yea, that's what I'm saying, uniform over the entire disk. I don't know if it needs a new diagram...isn't the diagram already earlier in the article just that? --Steve (talk) 17:38, 18 April 2008 (UTC)

Maybe the solid conducting disc problem can be analyzed as the superposition of discs with only a single conducting radius member (see Figure 2)? Then Faraday's law works for each component disc. If the rim is a perfect conductor one could argue that lines of current flow are radial, so each radial section is independent of the rest. Or, maybe not. The portion of return current traveling clockwise along the rim is subject to a radially inward Lorentz force tending to return it to the axle before it reaches the brush, while the couterclockwise component remains on the rim. I'm perplexed. Brews ohare (talk) 17:57, 18 April 2008 (UTC)

Again, I'm sure it's possible to think about this in a way that it works. Feynman's point, which this conversation makes me buy into more and more, was that trying to do that is more effort than it's worth, when the {Maxwell-Faraday + Lorentz force} approach is easier to apply and understand, and harder to screw up. He preferred to restrict the scope of the flux rule, with the payoff that the law would then be very easy to state and apply, and no elaboration and complication would be necessary to take care of Faraday's paradox...instead, you just say that the flux rule isn't going to apply there. The discussion of how to expand and/or state the flux rule so that it correctly explains Faraday's paradox is already the subject of that prior section, which you're welcome to expand on if you think it would help. --Steve (talk) 21:26, 18 April 2008 (UTC)

[edit] New example

I've added another example to the Faraday's law of induction page that makes the motional EMF thing clearer to me. As a result of this example, I conclude that a version of the Feynman "inapplicability" example on Faraday's paradox that uses a solid disc won't provide the example needed because it can be explained using the motional EMF approach. However, the example provided in the article cannot be explained this way, at least, not in any way I have thought of. Any comments? Brews ohare (talk) 04:57, 20 April 2008 (UTC)

[edit] Lorentz force

See if you want to comment upon Lorentz force. Brews ohare (talk) 02:36, 21 April 2008 (UTC)

[edit] Faraday's paradox

Sections of Faraday's paradox have been rewritten. This article could benefit from some kind editing. Brews ohare (talk) 22:37, 22 April 2008 (UTC)

[edit] Feynman revisited

Having thought about it some more, I've concluded that Feynman's counterexample and strong statement about basic physical law is on the money. I find that (i) "cutting the lines of flux" is hard to relate to the moving boundary problem in the flux integration, except in special cases, (ii) there is no necessary connection between the flux "linking" the circuit and the basic physics of moving electrons through the field; the connection is accidental to some special cases. Feynman's example is simpler using a sliding rectangle with a B-field in only a strip of the rectangle. That avoids confounding the flux calculation and the current paths. Then it is apparent that the flux rule is irrelevant to what happens. Brews ohare (talk) 16:36, 23 April 2008 (UTC)

The article looks fine to me. :-) --Steve (talk) 18:27, 23 April 2008 (UTC)

I have modified the Feynman example as described above. To me it is a cleaner example. Brews ohare (talk) 18:45, 23 April 2008 (UTC)

[edit] Moving magnet and conductor problem

I've rewritten the intro to Moving magnet and conductor problem. Having done that, I'm left feeling that the use of A is a much better approach than the E and B method, because E and B introduce the false dichotomy between electric and magnetic fields, mainly due to lumping the solenoidal and conservative E-fields together. These two components of E-field should be kept separate, as they have different origins and different behavior under switching of frames of reference. A cleaner formulation would leave out B-field and refer instead to A-field, while E--field would refer only to the conservative E--field. Of course, the gauge-transformation freedom makes you think that the potentials aren't "real", but one could argue that the E- and B-fields aren't real either - it's only forces and currents that matter. Differently put, we'd have the E-field redefined as only the conservative part and redefine the B-field as B = −∂ _t A + v × curl A . Would that fly better? (I'm not suggesting Wiki be rewritten like this, just thinking out loud.) Brews ohare (talk) 13:08, 2 May 2008 (UTC)

∂ _t A isn't, in general, solenoidal. It only is in the Coulomb gauge. If you read articles about the Coulomb gauge (e.g. here, which is also posted here), they do take full advantage of the fact that the solenoidal part of E comes from A and the conservative part from phi. But if you're not talking about the Coulomb gauge specifically, you can't say that. I mean, I guess you could tie your hands and say you're only going to use the Coulomb gauge forever, but that's not an especially convenient thing to do -- for example, the Lorenz gauge is more convenient in relativistic contexts.

Also, the redefinition B = −∂ _t A + v × curl A has the distinct disadvantage that B would stop being a vector field (a vector for each position), and rather becomes a function of position and velocity. The idea of defining fields in the first place, as explained e.g. in the introduction to Jackson, is that you get a conceptual separation between the creation of the fields and the response to the fields, so that you can compute the field without knowing anything about the particle responding to it. For example, that's why we can give quiz questions that say "What's the magnetic field arising from such-and-such current distribution?" If we redefined B according to the above, then that question wouldn't have an answer, it would depend on the velocity of the particle responding to the field.

I mean, I don't know for sure that our current set of definitions for electromagnetism are the best of all possible (equivalent) definitions. But they do seem to have some good reason behind them. --Steve (talk) 15:59, 2 May 2008 (UTC)

Thanks Steve. That is a very interesting discussion. Doesn't it impact the Moving magnet and conductor problem? The problem, as I understand it, is "Why do we have to deal with a magnetic explanation and an electric explanation in different frames?" when the observables of force and current are exactly the same. Why are different explanations necessary? My idea was that using A escaped this problem, because A could be used in every and any case. That is not the same thing as redefining B, however, so maybe I'm OK on this resolution of the problem. I guess I'd have to go a step further and say that the need for an E and a B is a problem the observer brings upon themselves if they insist on translating A into a E - B description. Brews ohare (talk) 18:02, 2 May 2008 (UTC)

I don't know if it impacts the article, I haven't been keeping up with your recent edits. I'm not quite sure I understand the questions/observations that you offer in your above paragraph. Most people are comfortable with the idea of stationary charges experiencing "electric but not magnetic forces", but if you'd prefer, you can just call everything an electromagnetic force, and use the electromagnetic tensor exclusively. Or, if you find A and phi to be more to your liking, you're welcome to use them too. :-P --Steve (talk) 21:54, 2 May 2008 (UTC)

Hi Steve: It seems fair to say that the Moving magnet and conductor problem doesn't push any buttons with you, eh? BTW, I posted a coordinate free centripetal force derivation. Brews ohare (talk) 22:33, 2 May 2008 (UTC)

Steve: I edited the footnote in Moving magnet and conductor problem to reflect your observations. Brews ohare (talk) 21:27, 3 May 2008 (UTC)

[edit] Explaining the centrifugal force

Hi Steve,

I see you are trying, as I recently did, to explain introductory physics to User:David Tombe. Just thought you might want to read the entries of Apr 28-30 on User talk:PhySusie.

--PeR (talk) 17:04, 2 May 2008 (UTC)

LOL, it all comes together. It's a small world. Thanks for the heads up! Hmm, as long as I'm still having fun, I suppose I'll continue to feed the troll. :-P --Steve (talk) 22:01, 2 May 2008 (UTC)

[edit] Gauss' law for gravity expansion/merge

Firstly, thank you for correcting my (appalling) typo in the Gauss' law for gravity article. Your modification makes it a lot more legible as well. I came across this article; Gauss's law for gravitational fields. It would appear to be concerning exactly the same subject and should probably be merged into Gauss' law for gravity. The current content is just the derivation of Gauss' law from Newton's law, but it appears to be more detailed and easier to follow than the current version, and also derives the integral version directly, which is what you start with when going the other way. For consistency and given you created the article, I wanted to check which version of the derivation of gauss' from newton's to keep (I can't judge the validity of either too well as I am a mathematician and only familiar with the formula, not its derivation).

I also was considering adding a subsection under the differential form section, showing how to derive it from the integral form briefly. The inverse is clearly not necessary as the method is entirely reversible. I would probably move the differential form to below the integral form as well, mostly because that is how I have seen it presented in most cases. Any suggestions would be well received, particularly regarding the duplicate article. If I have time I will put up the new derivation for now. – Ikara ^{talk →} 01:13, 1 June 2008 (UTC)

Hello!! I hadn't seen that article, despite looking. Thanks for pointing it out.

I'm not 100% sure what to make of the second half of Gauss's law for gravitational fields. It's not, as far as I can see, a derivation of Gauss's law (integral form) from Newton's law, since Gauss's law (integral form) is true for any surface with any mass distribution inside, whereas the article seems to be only talking about a spherically-symmetric surface with a point-mass in its center. On the other hand, if you change the last equation and its description appropriately, it would be a fine derivation of Newton's law from Gauss's law. In fact, it would then be the same as the section "Deriving Newton's law from Gauss' law" in Gauss' law for gravity, but with the assumptions spelled out worse, and the algebra spelled out better. I can incorporate those algebraic details when I get a chance.

Feel free to change the order of diff vs integral forms.

The derivation of differential from integral or vice-versa is the divergence theorem, no? Were you going to just say that, or were you going to put in a proof of the divergence theorem? I'd recommend against the latter; the proof of the divergence theorem belongs in the article divergence theorem, but probably not in other places. But if you want to spell out in full detail how the divergence theorem applies to this law, go for it. --Steve (talk) 01:44, 1 June 2008 (UTC)

Alright, I added the new section. It just shows the blindingly obvious (such as the relation between mass and mass density) and the application of div. theorem to the integral form of Gauss' law, but it does make the point that the two forms are equivalent absolutely clear, which can't be a bad thing. If you don't get to it by then, I'll merge the two articles tomorrow, making the necessary changes. I didn't add a merge tag as I didn't think the merger was particularly controversial. I would appreciate you checking what I've done sometime for any more careless mistakes. Interestingly, divergence theorem would appear to lack a proof, I may see to that sometime. It will be more familiar ground at any rate. – Ikara ^{talk →} 03:32, 1 June 2008 (UTC)

Hi again! Those were very nice edits. I agree that the merge tag wasn't particularly necessary, especially if they'll actually be merged so soon (I just put it in so any readers in the meantime would know that there were two articles). Speaking of which, I would not be able to merge the articles for at least a few days, so it sounds like you'll be doing it. Thanks! I would be happy to to check whatever changes you make. :-) --Steve (talk) 23:25, 1 June 2008 (UTC)

Hey, me again. I completed the merger, probably with some flaws, but it should make it easy for you to quickly check and correct it. I also found a slight mistake in one of the earlier equations, though not quite as bad as mine. The article is basically complete now, with the exception of any more applications that users can come up with. Glad you liked the last edits I made, hopefully these are even better. Thanks for the help. – Ikara ^{talk →} 03:58, 4 June 2008 (UTC)

Hello! Thanks for doing the merge. As I mentioned before, the proof of Gauss' law from Newton's law given on the other page was incomplete. Gauss' law says that for any V and any mass distribution, the equation holds, whereas the proof given only shows that it holds for a point-mass at the center of a spherical gaussian surface. I put in a (somewhat handwavey and visual, but widely used) field-line argument to complete it, and restored the other derivation in a show/hide box for those who might be interested in a more directly rigorous proof. Sound OK? Best, --Steve (talk) 21:55, 4 June 2008 (UTC)

As I expected... gah, never mind, thanks for fixing it. I've moved the mathematical proof out of the box after making it more readable (it is a very neat proof when you get your head around it) and gave a small illustration of the implementation of the Dirac delta function in this case to make it faster and easier to follow (took me a good five minutes as I've never encountered the function before). It may be a good idea for you to check it again given my current track record, but I'm pretty certain it's fine. I also reduced the nesting of sections a little as that was getting a bit messy. With all the work we've put into this article I just hope someone gets around to assessing it sometime. Thanks again – Ikara ^{talk →} 02:59, 5 June 2008 (UTC)

Well I'm happy. Thanks again yourself. --Steve (talk) 04:03, 5 June 2008 (UTC)

[edit] On Joaquin Mazdak Luttinger

Dear Sbyrnes321, the k.p perturbation theory, to which you have referred, is absolutely a minor thing; it does not merit to be mentioned in the opening part of the biography. Luttinger, together with Kohn, had however a major contribution towards formulating the transport theory in heterojunctions; the boundary conditions that they introduced for envelope functions are still in use. I believe that your addition should be removed, as k.p perturbation theory is absolutely and utterly a trivial thing: one just writes down the single-particle Schrödinger equation for the periodic part of a Bloch state and subsequently uses a series expansion of this function in terms of the same functions at k=0. There is absolutely nothing in the k.p perturbation theory worth the slightest mentioning. The situation would be different if the biography had already enumerated all the major contributions of Luttinger. Kind regards, --BF 12:52, 2 June 2008 (UTC)

Hello BF! I appreciate that you're bringing this to my attention here, rather than just reverting. Thank you!

I agree with you that, regarded as an advance in theoretical physics, it's trivial. On the other hand, it is quite widely used by physicists and engineers (because of its simplicity, in fact), and widely associated with Luttinger's name. All things considered, I would think that it should certainly belong somewhere in a proper biography, but not in the first two sentences. So what's to be done when the biography is only one sentence to start with?? I thought about this, and decided I'd put it in anyway, and hope that over time the biography would acquire enough additional information for that sentence to be properly balanced out.

It seems that you view the lack of balance as so outrageous that it outweighs any added information. That's fine; I'm sure you're more fit to judge this than me (I know very little about the rest of Luttinger's life). I would think the best solution would be to move the link out of the opening section, and into some other part of the article. Maybe I could make a "See also" section at the bottom, and put a link to the k.p article there? Or maybe a section titled "Physical theories that Luttinger has contributed to" with a bulleted list, including Luttinger liquid, heterojunctions, k.p theory, and whatever else? Do any of these sound reasonable? Any other ideas? :-) --Steve (talk) 18:36, 2 June 2008 (UTC)

Dear Steve, you are welcome. I believe that the k.p perturbation theory should be referred to in a section with such heading as you suggest; reference to it just in the first paragraph amounts to giving it undue prominence. Incidentally, in the event that you have the time to extend the entry, I recommend you to consult Luttinger's obituary by Kohn et al., which I have cited in the bottom of the entry; it is a very nice obituary, written by no less than two Nobel laureates. Such extension will also enable you to move the sentence concerning the k.p perturbation theory to a less prominent place. Naturally, you could also consider to create an entry on the k.p perturbation theory, to which you can subsequently make a link from within Luttinger's biography. Kind regards, --BF 19:45, 2 June 2008 (UTC)

OK, I tried to make changes along those lines. Please let me know your thoughts. :-) --Steve (talk) 21:07, 2 June 2008 (UTC)

It looks very good! Did not realise that there was already an entry on k.p method, written by you, on 30 May, to boot. Kind regards, --BF 21:14, 2 June 2008 (UTC)