Wikipedia talk:WikiProject Physics/Archive November 2008

Particle infoboxes

I'm filling various particle infoboxes and I have a few questions.

Gravitons

• What is are their antiparticle? Itself or antigravitons?
• Is it a gauge boson?
• Who theorized it and when was it proposed?
• Does it have a symbol?

Gluons

• Who theorized them, when were they proposed, and when were they discovered?

Mesons

• Right now it says that they strongly interact. But don't they also interact through the other 3 forces as well (Weak, Electric, Gravity)?

More will follow soon.

Headbomb {^ταλκ_{κοντριβς} – WP Physics} 05:50, 31 October 2008 (UTC)

About gravitons. Typically they are considered to be the "quantized" version of the metric field. As such has spin-2 (and thus is boson.) The metric field has the diffeomorphism group as a gauge group, hence they are gauge bosons. Since it is just the metric field it typically uses g or G as a symbol. (sometimes decorated in some way to indicate its quantumness.) It has been around for a while now. For a detailed history see [1]. Apparently, the term was first coined in the 1930's by Blokhintsev and Gal’perin.(TimothyRias (talk) 09:14, 31 October 2008 (UTC))

The term "gluon" was first used in the paper of Gell-Mann published in 1962. It was applied for carries of some abstract field. The term stuck, and was later used as the name of QCD field quanta. Ruslik (talk) 11:34, 31 October 2008 (UTC)

For gluon discovery, see three jet event. Re mesons... Yes, they interact weakly and this is important in many of their decays. The charged ones interact electromagnetically. And yes, everything interacts with gravity. -- SCZenz (talk) 12:10, 31 October 2008 (UTC)

Like the photon, the graviton has no charges to be negated by the charge conjugation operator. So it is its own anti-particle. JRSpriggs (talk) 12:12, 1 November 2008 (UTC)

Dirac's LNH - stub of low importance

The current rating for Dirac large numbers hypothesis on the assessment scale is as a stub of low importance. Significant revisions followed the edit war with 'scottfunkhouser' and the article is now more than just a stub. I'm wondering how to get it reassessed. Also I don't agree with the 'low importance' rating. LNH might be just a 'fringe' theory but it has quite a dynamic history, it has engaged the energies of seminal figures like Dirac and Dicke, it has impacted on the mainstream in significant ways (particularly in the philosophy of science e.g. formulation of the 'Anthropic coincidence') and it continues to be a source of interest and controversy even for mainstream journals. I hope others here will continue to monitor the article. I was a bit too emotionally involved in the edit war with 'scottfunkhouser' and I now want to get it off my hands. Thanks. Lucretius (talk) 23:48, 2 November 2008 (UTC)

Apart from good-article and featured-article designations, there's no formal assessment procedure. If you think an assessment is inaccurate, change it. :-) --Steve (talk) 00:08, 3 November 2008 (UTC)

I just reset it to physics start class, mid importance, which I think is closer. Wwheaton (talk) 04:17, 3 November 2008 (UTC)

OK - thanks for that. I'm satisfied with 'mid importance' but I don't agree with 'start class'. However, I'm not going to rate my own work on the assessemnt scale so I'll leave it as is. Hopefully others will change the rating upwards or else contribute something classy to it. Lucretius (talk) 06:33, 3 November 2008 (UTC)

I confess I was being conservative with the "start" class rating, and thinking "at least start class"—not having time to really review it carefully. Let's see what other editors think. Wwheaton (talk) 07:47, 3 November 2008 (UTC)

MECO

Magnetospheric eternally collapsing object has been nominated for deletion at WP:AFD 70.55.86.100 (talk) 09:43, 3 November 2008 (UTC)

Opinion requested on Kepler's laws

Could someone have a look at Kepler's laws? I think the article needs to be rigorously pruned in the amount of mathematical proofs, since they are not illuminating the concepts, but rather tediously proving concepts that are rather easy to visualize. But maybe I'm seeing it wrong. Please discuss on Talk:Kepler's laws of planetary motion. Han-Kwang (t) 21:00, 19 October 2008 (UTC)

Has anybody considered using {{hidden}}? -- Army1987 (t — c) 12:07, 21 October 2008 (UTC)

I agree, I've always been fond of show/hide boxes for proofs that are relevant but not central. See for example here or here for places I've used these. :-) --Steve (talk) 19:01, 21 October 2008 (UTC)

The sentence "Thus, not only does the length of the orbit increase with distance, the orbital speed decreases, so that the increase of the orbital period is more than proportional" makes no sense. I can't see how something can be "more than" proportional, surely proportionality is a Boolean concept._{this appear to have has been fixed} The article needs more than pruning, it needs re-writing for the layman. By all means have derivations, but restrict these to a separate section and make the rest of the article readable by all. Jdrewitt (talk) 20:15, 21 October 2008 (UTC)

I agree. I would suggest dividing the article into two parts, 1) discussing qualitatively preferably using potential plots in the context of inverse square law central forces, and some immediate implications of the laws. 2)the mathematical details. At least I don't see the point of all that content discussion on ellipses in general. A simple link to the main article on ellipse like this should be enough. Also as suggested above, the use of {{hidden}} would bring a lot more clarity. --Fatka (talk) 03:07, 5 November 2008 (UTC)

Would you fellows please mention this on Talk:Kepler's laws of planetary motion where currently a two persons are splitting hairs over whether how tangential accelerations should be dealt with in the mathematical description? Han-Kwang (t) 09:09, 5 November 2008 (UTC)

I have started a discussion at Talk:Kepler's_laws_of_planetary_motion#Template_message_math2english_added. This is not the first time such a suggestion has been made and not heeded. I have mentioned the possible use of {{hidden}} but it seems to be falling on deaf ears. Jdrewitt (talk) 20:55, 8 November 2008 (UTC)

Thanks steve for your input over there. You're much better a putting your point across than me. Jdrewitt (talk) 09:34, 9 November 2008 (UTC)

I made some edits to the introduction to the three laws to make it more comprehensible and reorganized the Talk page into more relevant sections. Hopefully a little structure will lead to some creative criticisms and consensus. Fatka (talk · contribs) 00:33, 10 November 2008 (UTC) —Preceding unsigned comment added by Fatka (talk • contribs)

Tagging diagrams in need of correction

In the article Fictitious force, several gif diagrams have been added recently. I found that they are incorrectly depicting fictitious forces. Although the discrepancies are subtle, they end up conveying the wrong concept. I have posted this on Talk:Fictitious_force#Possible_errors. But how do I tag the individual images to get the attention of the creator or Wikipedia editors? I have posted this on Help desk, so far no one has replied neither on Help desk or on the article Talk page. What should be the next step? Fatka (talk · contribs) 01:06, 10 November 2008 (UTC) —Preceding unsigned comment added by Fatka (talk • contribs)

If I saw a problem in Image:Accelerating car.PNG for example (not saying whether it has one or not), I would click on the image and go to its own page. I would look at its revision history and see that it is the work of Brews ohare (talk · contribs). I would go to his talk page and leave a message about said problem. JRSpriggs (talk) 18:04, 10 November 2008 (UTC)

Thank you for the hand holding. I started editing extensively only recently. :) much appreciated. -- Fatka (talk · contribs) 18:43, 10 November 2008 (UTC) —Preceding unsigned comment added by Fatka (talk • contribs)

I tried to find the user page of the uploader, but it seems he/she doesn't have one. What should be the next step? -- Fatka (talk · contribs) 18:54, 10 November 2008 (UTC) —Preceding unsigned comment added by Fatka (talk • contribs)

Unfortunately, this user is not on our wiki. He is on the commons. I do not know what is the best way to reach his talk page, but you can click [2] to get there. JRSpriggs (talk) 21:12, 10 November 2008 (UTC)

FAR for photon article

The photon article has been nominated for a Featured Article Review, due to concerns about lack of references and other issues. The article may no longer meet the FA criteria. Please comment here. Thank you.—RJH (talk) 19:35, 11 November 2008 (UTC)

e-p scattering/annihilation

There's these two images on wiki. Now it seems to me that these just aren't right. I'm gonna ask the graphic labs to fix them, but I just want to make sure that I don't end up looking like idiot in doing so.

What I'd propose for the fix is this:

e+        e-

     γ

e-        e+

instead of

e+        e+

     γ

e-        e-

Is that all right?

Feynman Diagram of Electron-Positron Annihilation

For one thing, when people talk about "electron-positron annihilation", they're not talking about either of those diagrams, they're talking about this one on the right. Your diagrams (regardless of the labels) both describe scattering. --Steve (talk) 01:28, 12 November 2008 (UTC)

Thanks for pointing that out. I should've picked that up, but for some reason I didn't.

• Concerning the EP annihilation diagram, isn't the "middle part" sorta useless? Why not simply go for a single vertex diagram?
• I am correct in assuming the proposed correction for the scattering diagram is fine?

Headbomb {^ταλκ_{κοντριβς} – WP Physics} 01:44, 12 November 2008 (UTC)

I'm not sure about your proposed changes. Here's what I would do.

(1) Make it clear that time goes from left to right. This could be done by editing the diagram, inserting a little arrow and label, as in Image:Feynmann_Diagram_Gluon_Radiation.svg. It could also be done in the caption. Maybe you were assuming that time was going bottom to top? Both conventions are used (for example look at the figures in Feynman diagram), but I think whoever made this diagram wanted time to go from left to right.

(2) Sort out the directions of the arrows. A proper Feynman diagram should have arrows pointing opposite the physical motion of positrons, and the same as the physical motion of electrons. If you do it right, every vertex has one arrow in and one arrow out. Anyway, I think you would want to switch both of the top arrows in both of the diagrams.

To answer your other question, for the annihilation diagram, the middle part can't be thrown out. The rules of Feynman diagrams say that you're only allowed to use certain vertices in your diagrams (the list of allowed vertices is determined by the standard model Lagrangian). The vertex where two electrons and two photons come together at one vertex, isn't on the list of allowed vertices. --Steve (talk) 05:39, 12 November 2008 (UTC)

I mean the single vertex diagram
e⁻
+
e⁺
→
γ⁰
, not
e⁻
+
e⁺
→
γ⁰
+
γ⁰
. See [3] and [4] for what I mean.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 19:38, 12 November 2008 (UTC)

Oh. An electron and positron have to annihilate into at least two photons, not just one. Otherwise it's impossible to satisfy energy-momentum conservation. To see this, put yourself in the reference frame where the total initial (electron+positron) momentum is zero...then the outgoing photon would be stuck with zero momentum but lots of energy. :-) --Steve (talk) 19:46, 12 November 2008 (UTC)

Also such designations as
γ⁰
should be avoided, because it is a gamma matrix. Use
γ
. Ruslik (talk) 20:12, 12 November 2008 (UTC)

Well there's a lot of notations that looks likes a lot of other notation in physics, so that's rather moot to argue that we shouldn't write the charge on photons when its clear we're talking about particle processes. I mean, we wouldn't argue against writing He⁺ because it "might be" confused with the interaction of Hydrogen and an antielectron :P. As for the single photon vertice, I'm not quite sure what you're getting at. If you're arguing that the single photon diagram is wrong, then wouldn't the diagram posted by Sbyrnes up there be twice as wrong, since there would be two reference frames where a photon is stuck with zero momentum but non-zero energy. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 02:49, 13 November 2008 (UTC)

And yes I'm making no distinction between real and virtual process, 'cause I'm crazy like that. If you're talking about pair annihilation in real processes then we're on the same page. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 03:01, 13 November 2008 (UTC)

I think we're talking past each other, and also getting off topic. I'm taking the liberty to move this entire thread to User talk:Headbomb#e-p scattering/annihilation. --Steve (talk) 03:49, 13 November 2008 (UTC)

Fractal cosmology

Fractal cosmology has been nominated for deletion at AfD. 76.66.192.6 (talk) 05:30, 13 November 2008 (UTC)

Scale relativity

Scale relativity has been nominated for deletion at AfD. 76.66.192.6 (talk) 05:30, 13 November 2008 (UTC)

Help for list of mesons

I'm currently expanding the List of mesons to be something similar to the List of baryons. Right now I'm identifying the vector mesons equivalent of the pseudoscalar mesons and I'm having some trouble. If you could head over to Talk:List of mesons#Completing the tables and give a hand, that would be much appreciated.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 05:30, 13 November 2008 (UTC)

Subsectioning of the Template:Infobox Particle

It was suggested during a PR that the physical properties portion of {{Infobox Particle}} could be formed into a subsection with its own header. What do you think of this suggestion? The template could also use a little color. Thank you.—RJH (talk) 17:43, 13 November 2008 (UTC)

The centrifugal force debate

Could somebody have a look at the centrifugal force page with a view to shortening it and unifying the topic into one single article. I have given up trying. The article has been split and forked as a result of different interpretations surrounding a certain dilemma regarding the radial planetary orbital equation. This hasn't been helped by the fact that as well as the disagreements over how to interpret the dilemma, there are also those editors who refuse to acknowledge the dilemma at all.

The radial planetary orbital equation in question is,

A = B + C

Everybody agrees that C is centripetal force, and that if A equals zero we will have circular motion.

But the argument gets bogged down in pointless semantics about whether or not A is called "radial acceleration". OK, so call A Alfred. If Alfred is zero then we will have circular motion.

But the argument then gets bogged down in pointless semantics over what to call B. Some say it is centrifugal force. Others say it is only centrifugal force in the co-rotating frame of reference. OK, so call it Billy.

The point is that when we have circular motion, then Alfred will be zero and Billy and Centripetal force will sum to zero. If we ever get rid of Billy, then Alfred will come back again and we won't have circular motion.

We cannot therefore have a circular motion that only involves centripetal force and nothing else. This fact has serious implications when it comes to extrapolating the rotating frame transformation equations to objects that are at rest in the inertial frame as viewed from the rotating frame of reference. That is were the dilemma lies, because making this extrapolation leads to an absurdity which is actually published in some textbooks.

Somebody needs to go there and take a look. There is only one universal centrifugal force, and anybody who thinks otherwise lacks an overall comprehension of the topic. David Tombe (talk) 18:24, 14 November 2008 (UTC)

Physics article replaced

Please discuss this edit from a couple months ago, which replaced Physics with a "Development Article." Is the current version an improvement? 200.72.246.90 (talk) 11:24, 16 November 2008 (UTC)

Vector space

I'm currently working on vector spaces, which has a passage reading

The solutions to various important differential equations can be interpreted in terms of Hilbert spaces. For example, a great many fields in physics and engineering lead to such equations and frequently solutions with particular physical properties are used as basis functions, often orthogonal, that serve as the axes in a corresponding Hilbert space. As an example from physics, the time-dependent Schrödinger equation in quantum mechanics describes the change of physical properties in time, by means of a partial differential equation determining a wavefunction.

I personally don't have access to physics books right away, so I'd like to kindly ask whether somebody around could provide references for the facts. Probably it's not a big deal for you guys ;) I think I could come up with some math book covering the claims, but I think a physics book for a physics statement might be better. Thanks, this is about the last bit preparing the article for WP:GAN. Jakob.scholbach (talk) 14:59, 17 November 2008 (UTC)

I'll have a look later today. I think Kreyzig (a popular engineering mathematics text probably could yield a good reference for the first statement. The second statement should be referencable from any QM textbook. I'll check my copy of Griffiths. (TimothyRias (talk) 16:03, 17 November 2008 (UTC))

Thank you, I appreciate it. Please be sure to make the ref precise (with a chapter or page number). Jakob.scholbach (talk) 16:31, 17 November 2008 (UTC)

Thanks again, Timothy, for your swift help. I have now nominated the vector space article for WP:Good article nomination#Mathematics. I'd be thankful if people around could have a look. Jakob.scholbach (talk) 09:30, 18 November 2008 (UTC)

Taskforces

I noticed that WP Relativity, WP Fluid dynamics and WP Acoustics all have low level of participation, if any. I would propose making them taskforces rather than WikiProjects due to the relatively low number of articles under their wings. I think participation in them would increase if they were made taskforces, as well as make it easier to coordinate efforts. Any thoughts?

I'm also posting this on the relavant WP talk pages.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 22:20, 10 November 2008 (UTC)

Well no one commented on anything, so I'll just go ahead and move them to Wikipedia:WikiProject Physics/Taskforces/Foobar. I've updated the banner to handle them as taskforces. Parameters are relativity=yes, fluid-dynamics=yes, and acoustics=yes. Headbomb {^ταλκ_{κοντριβς} – WP Physics} 13:13, 24 November 2008 (UTC)

I've made the bot request [5] to tag articles as being part of the taskforces.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 13:29, 24 November 2008 (UTC)

Hmm. I'm not sure of some of the side effects this is having. Some of the articles that were clearly inside the scope of these projects are not really within the scope of WP physics. As example take the article 3D ultrasound, it clearly was in the scope of WP acoustics, but I don't really see it as falling within the scope of this WP. (TimothyRias (talk) 14:51, 25 November 2008 (UTC))

Well 3D ultrasound article sounds (no pun intended) like something that's completely compatible with WP Physics. It's an imaging technique, which is IMO, just as much under the scope of WP:PHYS than the MRI article is. Anyway, it's quite possible that some ill effects followed the "merger", but these wikiprojects are inactive (last edits on these pages are months away), so there's very little harm done. Plus, someone else could always restart the old projects if interest is there.

None of these articles are tagged with importance ratings anyway, so if they aren't part of WP Physics, they'll be untagged over the next months.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 21:40, 25 November 2008 (UTC)

Found these two images, which I find wonderful, but I don't know where to place them.

(Complete Omega- decay chain) (discovery of the Omega-)

I've placed the links on the Omega baryon page, but it seems to me that the one with the complete decay chain should be on more pages than that one.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 23:45, 25 November 2008 (UTC)

I realize now that it's the same image.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 23:59, 25 November 2008 (UTC)

Statistical physics / mechanics / thermodynamics

There are currently three articles on this topic - Statistical physics, Statistical mechanics and Statistical thermodynamics - which seems to be at least one too many. Would it be worth reorganising the information on this topic? If so, what would be the best approach?

(I'm asking this here rather than on each article's own discussion page as I think the issue needs people with a general overview of the topic as a whole. I'm also cautious about just doing it myself, as it isn't really my area. As an added advantage, dealing with the question should allow us to get rid of the final Top-importance Stub-class article!) Djr32 (talk) 13:14, 22 November 2008 (UTC)

I've merged the first two but more work is needed. Abtract (talk) 19:21, 22 November 2008 (UTC)

Is that a vote for merging Statistical physics with Statistical mechanics, and keeping Statistical thermodynamics separate? I'm not sure I agree - I've always seen Statistical thermodynamics as being another name for Statistical mechanics. The two articles seem to cover the same area, though the Statistical thermodynamics article is a nice introduction while the Statistical mechanics article is quite heavy on equations. I'm not sure about Statistical physics. Sometimes it seems to be used as another name for the same thing, but sometimes (as Jheald said on Talk:Statistical_physics) it seems to be used to cover a wider range of topics - including, but not limited to, stat mech. What does anyone else think? (For anyone who wants it, the old Statistical physics article is here) Djr32 (talk) 22:08, 24 November 2008 (UTC)

I am pretty sure Statistical mechanics and Statistical thermodynamics are more or less synonyms. But Statistical physics is wider, including topics that are not related to thermodynamics at all, such as complex networks. Have a look at the list of invited speakers in StatPhys 23: topics 10 and 11 are clearly far from the usual Statistical mechanics domain, but are considered bona fide Statistical physics areas. --Daniel (talk) 10:17, 25 November 2008 (UTC)

Following this discussion, I've resurrected the Statistical physics article, and tried to expand it a bit to show why it's not a synonym for Statistical mechanics. I still think there's work to do, both on expanding the Statistical physics article and perhaps by merging Statistical mechanics and Statistical thermodynamics. Djr32 (talk) 11:26, 30 November 2008 (UTC)

I work in statistical physics and I'm very much accustomed to see the terms "statistical physics" and "statistical mechanics" being used as synonymous in books and articles. I don't think there's a real distinction. One could say that, rigorously, statistical mechanics should be restricted to the study of mechanical systems with many degrees of freedom. But some of the most important models studied under the guise of statistical mechanics aren't mechanical models. The Ising Model, for example, is not a mechanical model, classical or quantum. It's not a dynamical model with a lagrangian and Euler equations of motion, like a gas, and it's not a quantum model, with Heisenberg dynamics, like the Heisenberg model. I frequently call what I do "statistical mechanics" and it's not about mechanical models. (sorry, forgot the signature) Rafael Calsaverini (talk) 16:25, 13 June 2011 (UTC)

Assessment update

Assessment progression graph

Keep up the good work people.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 07:55, 27 November 2008 (UTC)

Category:physicists

I went through Category:physicists and tried to shove everyone in a nationality, but I've hit a wall. If anyone of you knows from which countries the remaining people are, please shove them where they belong.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 06:07, 29 November 2008 (UTC)

Two are under P but I didn't know how to correct it. Also Chilean shows (0) but there is one (I didn't check SA.) [+] Chilean physicists (0) [+] South African physicists (0) Abtract (talk) 11:30, 30 November 2008 (UTC)

Gilbert Jerome Perlow

I just created the page about Perlow, so if you have anything to add to it, go right ahead.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 22:33, 29 November 2008 (UTC)