Talk:Quantum electrodynamics

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Page on the Nobel Prize official site http://www.nobel.se/physics/laureates/1965/feynman-bio.html shows this as the 1965 Prize in Physics

I didn't initiate the attention notice, but the guidelines state that it is alright to put the notice on the talk page. Interested parties will note that the category will alphabetize this entry correctly. Ancheta Wis 22:38, 31 Dec 2004 (UTC)

Contents

[edit] Expansion request

 Please help improve this article or section by expanding it.
Further information might be found on the talk page or at requests for expansion. (January 2007)

A lot of information on the history of this theory should be pulled in here. See e.g. Quantum_mechanics#History. -- Beland 05:50, 14 August 2005 (UTC)

[edit] From PNA/Physics

  • Quantum electrodynamics - I fixed the broken LaTex formula to conform to the author's apparent intent. I'm not sure if the "D" in the sentence following the formula should also be slashed. Could someone who knows QED double-check this please? --Ortonmc 23:22, 13 Sep 2003 (UTC)
cleaned up some Latex, but it still needs a lot of work lethe
I moved this from the "mathematics" section. Paul August ☎ 18:33, Jun 5, 2005 (UTC)

</math>

[edit] Persistent... idontknowhattocallit

The same anon that's been going around vandalizing other theoretical phyisics related articles, has apparently settled on this page, and while I wouldn't call its edits outright vadalism, I would say that its past history makes me doubt its seriousness, seems more like it's picked an article where vandalism wouldn't be very likely to be noticed, and stuck with it

My opinion is that you should look up the information in the citation before accusing the person of vandalism. Edit: ...though it seems that the user has not made a strict citation or reference, making a check quite difficult to do. I'll see what I can dredge up. In the meantime, let's not treat something as vandalism until we see genuine reasons to do so. Lucidish 01:42, 5 January 2006 (UTC)
The citation for the Feynman quote that's floating around is James Gleick's "Genius: The life and science of Richard Feynman", p348. Lucidish

The editor was a notrious POV-pusher, Licorne. I have re-removed the quote, because as it stands it sounds like Feynman repudiated QED in his later life, which is, as best I know, not true. –Joke 16:43, 14 March 2006 (UTC)

He didn't repudiate it, but even in his Nobel acceptance speech he called the theory he'd won the prize for a bit of a cheat or something to that effect. This quote doesn't seem to be inappropriate to me, I'm going to reinsert it, but with a small amount of explanation.WolfKeeper 17:21, 14 March 2006 (UTC)

Fair enough. I'm happy with your version. –Joke 17:28, 14 March 2006 (UTC)

[edit] Every Possible Path?

From article "In fact, according to QED, it takes EVERY possible path between the start and end points."

I think that the claim that it takes EVERY possible path is Feynman's Many World's interpretation of quantum mechanics and not a necessary component of QED.

IRC Feynman claimed only the consistent histories interpretation of quantum mechanics which is a stronger claim than many worlds, since it makes no claim for non observable universes, only those that reconnect back with ours.WolfKeeper 13:07, 23 February 2006 (UTC)

However, in order to do some of the calculations in QED, which, according to the book "QED" cited on the page, can be done by drawing pictures on a 2d access of space and time, Feynman diagrams. Now in order to do the calculations you need to know every possible path it can take before you compute the probability of it taking a certain path (which is the experimental evidence of QED), but that is not the same as it taking every possible path.--MobyDikc 23:43, 8 February 2006 (UTC)

Yeah, it is, due to destructive/constructive interference. If the particle didn't go every which way you wouldn't get interference like that.WolfKeeper 13:07, 23 February 2006 (UTC)

[edit] We Need a Picture of the Basic Vertex!

One of the simple beauties of QED is that the trilinear term in the Lagrangian corresponds to a vertex in a Feynman diagram where an electron absorbs a photon (or emits one, or etcetera depending on how one views the vertex). This should be explained, and there should be a nice picture of this basic vertex. Right now only some fancier Feynman diagrams are shown... the simplicity of the theory is not being explained!

I would improve this article right now but I'm busy preparing a talk and I just wanted a picture of this vertex...

John Baez 10:32, 23 February 2006 (UTC)

John, it is very good to see someone of your calibre take a close interest in this important article on the "jewel of physics." Although I am no physicist (but do own a copy of Feynman 1985), forgive me for making the following possibly rash and uninformed remarks:
  • Someone please do a yeoman's job of communicating the essential "simplicity" of QED.
  • A subject this rich and this important deserves a longer entry, period.
  • Beautiful physics (GR, Maxwell's EMF, Boltzmann) often culminates in beautiful equations, especially when these are cast in Planck units. Why does no beautiful equation command pride of place in expositions of QED?
  • Wikipedia should include a killer intro to Feynman diagrams, a splendid instance of science done by semiotic means.
  • The last word re renormalization has yet to be written. One day the physics and math will reach a state that Feynman would applaud.202.36.179.65 19:33, 25 March 2006 (UTC)

[edit] Feynman diagrams

There are some nice illustrations of Feynman digrams with loops but no accompanying explanatory text. Could someone please remedy this ommission?

[edit] "See Also" list

The "See also" list is very long; in my opinion there is a lot there that isn't directly relevant to quantum electrodynamics. E.g.: Basics of quantum mechanics, Photon dynamics in the double-slit experiment, Schrödinger equation, and Theoretical and experimental justification for the Schrödinger equation. Paring down this list might help focus people on the more relevant items. (I'm not confident enough to be bold here.) HEL 02:30, 8 October 2006 (UTC)

I agree, as well with the pages on Standard Model, Positronium, and Photon polarization. Watchayakan 05:14, 14 November 2006 (UTC)

[edit] Accuracy

Predictions of QED agree with experiments to an extremely high degree of accuracy: currently about 10−12 (and limited by experimental errors)

What does this 10−12 mean exactly? Significance? This seems unclear to me. --Jaapkroe 11:40, 28 October 2006 (UTC)


This means "Theory and experiment agree with each other to within one part in a million million." This is a completely standard scientific terminology, but a translation into words might be nice for a broader audience.

My complaint with this statement is with the "and limited by experimental errors". In QED most of the experiments are performed in particle accelerators which pin down particle-particle interactions to a very high level. In MANY cases the experiments are far more accurate that the QED predictions because to get better and better predictions, more and more higher order possible interaction pathways have to be considered. Eventually you just give up because your computer isn't big enough to work them all out. You just say "I've got the most imporatnt ones and I'll just ignore all the rest".

So I'd very much like the slur on experimental physicists removed. Please.

131.111.8.96 16:31, 6 November 2006 (UTC) Will (an experimental physicist)

[edit] Huhsaywhat?

I chanced upon this subject researching a midterm essay for science... can't say I very well know half of what it means. Any clue where to start, cause obviously this isn't exactly 1st grade science class. 68.239.57.153 16:41, 24 January 2007 (UTC)

The best place to start for non-physicists is by watching the 4 lectures that Feynman gave in 1979. They are available here: http://www.vega.org.uk/video/subseries/8 It'll take you 5 hours to watch all of them, but he explains QED (and a lot of other physics concepts) in a novel way without getting technical, and there's almost zero math involved. I'm not a physicist and I picked up a good understanding of what QED is all about from these. Just make sure you pay attention to what's going on. And feel free to ask questions at my talk page if you get confused. Wikipedia brown 02:32, 25 February 2007 (UTC)

[edit] Rewriting Request

After reading some of the text on the page I realise it is more like an essay than a encyclopedic entry. I wonder if someone can do something about it. 220.238.162.141 12:11, 21 March 2007 (UTC)

[edit] Mathematical Consistency of QED?

I think the article could be improved by providing the current expert's view (or range of views perhaps) on the question raised by Feynman (and many others!) in his 1985 popular level QED book (already referenced in the current version of the article; the book is based on lectures given 82 or 83 by the way?) which is (quoting Feynman): "It's surprising that the theory still hasn't been proved self-consistent one way or the other by now; I suspect that renormalization is not mathematically legitimate." In fact I came to this article looking for an answer to this question. What's confusing me is that somewhere or another I think I recently (last couple of years) read that QED had been shown to be inconsistent (perturbation series eventually diverges); however when I try to track this down all I can find is Dyson's 1952 article which as far as I can tell (as a non-expert) simply suggests that it is very likely that the series (as it was formulated at the time; has there been further progress?) almost certainly eventually diverges (and this would of course have been known to Feynman, having appeared 30+ years earlier). While this is probably of no importance for doing physics, it is (I think) extremely interesting mathematically, and also interesting in terms of philosophy of physics. So ... what's the story regarding mathematical self-consistency of QED? Jtrbnsn 16:38, 14 October 2007 (UTC)

[edit] Free evolution of the electromagnetic field?

Quick question--at the end in the section 'In Pictures' it describes the second boxed equation as describing the free evolution ot the electromagnetic field, is this correct? As the equation involves the electron/positron fields is the term 'free' appropriate? Thanks, Ivanivanovich (talk) 15:18, 24 January 2008 (UTC)

[edit] Contradiction

On Precision tests of QED it says

Quantum electrodynamics (QED) is the most stringently tested theory in physics (after special relativity which currently is tested [1] to 10-21 - Michelson-Morley experiment: 10−4, Hughes-Drever experiment: 10−16, trapped atoms experiments: 3×10−22)

, whereas here it says

This makes QED the most accurate physical theory constructed thus far.

—Preceding unsigned comment added by Rangek (talk • contribs) 20:50, 25 January 2008 (UTC)

Discrepancy explained Omeganumber (talk) 03:13, 1 March 2008 (UTC)

This updated edit detracts from the importance of QED and looks to me almost blasphemous, however it was necessary to avoid confusion. Omeganumber (talk) 12:00, 1 March 2008 (UTC)

I've undone the edits because the situation remains muddy. What does "subjective precision" mean? How is it determined? Who determined it? Where is the reference for that?  --Lambiam 20:00, 1 March 2008 (UTC)

It is obvious the understanding of the indeterminacy of experimental accuracy at a quantum level can not be explained in simple terms to confirm QED is the most accurate physical theory constructed thus far (or refute ). I would revert the article, but will leave that to another user, as I was tempted to insert a well known acronym used by Feynman. Omeganumber (talk) 20:25, 1 March 2008 (UTC)


The problem has now been resolved; 80.192.42.32 has replaced "most accurate" by "one of the most accurate physical theories" (also at Precision tests of QED).  --Lambiam 11:01, 3 March 2008 (UTC)