User talk:Jim.belk

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Welcome!

Hello, Jim.belk, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are a few good links for newcomers:

I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (~~~~); this will automatically produce your name and the date. If 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. Again, welcome!  Robdurbar 10:28, 14 February 2006 (UTC)

Contents

[edit] Image:Link Crossings.png

Hi. It looks like you may have made the above image yourself: if this is the case, please say so on the image page. If not, please give its source so that its copyright status can be determined. Failure to do this may result in the image being deleted. Thanks, David Mestel(Talk) 08:47, 25 July 2007 (UTC)

[edit] Orion (mythology)

Thanks, that was much more useful than FAC; I think I've responded, at least in dealing with Hesiod's version. Let me know what you think (and if you do see any grammatical or spelling errors, please fix them). Septentrionalis PMAnderson 15:52, 6 August 2007 (UTC)

[edit] The Quadrature of the Parabola

Thanks for creating this article as it is a very useful source of information on the theorem. I was wondering why I had not seen it before, then realized that it was created on 13 August 2007. Here is a question: is Archimedes shown demonstrating the quadrature of the parabola on the 1983 Greek postage stamp in the article Archimedes? (the image is also at [1]). At one stage I was fairly sure of this, then had some doubts. --Ianmacm 17:49, 13 August 2007 (UTC)

Thanks for your reply. I have changed my mind and don't believe that it is intended to be the quadrature of the parabola. The apparatus behind him on the stamp is definitely illustrating the principle of buoyancy, but the geometrical diagram is more of a mystery. --♦IanMacM♦ (talk to me) 06:38, 14 August 2007 (UTC)

[edit] Request for edit summary

Could you please use the edit summary more often? Thanks. :) Oleg Alexandrov (talk) 17:32, 18 August 2007 (UTC)

I replied on my talk to keep all conversation in one place. Oleg Alexandrov (talk) 17:47, 18 August 2007 (UTC)

[edit] Did you know...

Updated DYK query On 22 August 2007, Did you know? was updated with a fact from the article Word (group theory), which you created or substantially expanded. If you know of another interesting fact from a recently created article, then please suggest it on the Did you know? talk page.

--Allen3 talk 13:46, 22 August 2007 (UTC)

[edit] System of linear equations

I think you did an excellent job on system of linear equations (but what is a flat, in the sentence "the flat for the first equation can be obtained by …" in the last section?). It may be a basic topic, but those are often the most difficult articles to write. Thanks very much. -- Jitse Niesen (talk) 07:49, 29 August 2007 (UTC)


Jim, it is possible to preview your changes before saving them and thus avoid producing dozens of versions. Xxanthippe 22:33, 1 September 2007 (UTC)

[edit] Thank you!

Hi, Jim.belk. Thank you very much for writing the new article Euclidean subspace. The images are very nice, and add a great deal to the article. It's carefully and methodically written, and very clear.

I did make a number of small changes (mostly correcting typos, inserting "of" where it was missing, adding a couple of wiki-links where they seemed appropriate, etc.) Anyway, you might want to take a look at it to be sure I didn't mess anything up too badly. Oh – there was one spot near the end where you used "union" and "sum" as synonyms … I wasn't certain what you meant to say there, so I didn't make a change, but you might want to think about it a little.

Thanks again for an excellent article! DavidCBryant 14:48, 3 September 2007 (UTC)

[edit] Footnotes

At System of linear equations you added a footnote reading as follows:

"Linear algebra, as discussed in this article, is a very well-established mathematical discipline for which there are many sources. Almost all of the material in this article can be found in Lay 2005, Meyer 2001, and Strang 2005."

I understand the impulse, but the note reads like defense against an anticipated attack from WP:V nuts demanding that every sentence have three "inline citations". The purpose of references and citations is to benefit the reader, not distract. WikiProject Mathematics, in collaboration with other like-minded projects, developed the Wikipedia:Scientific citation guidelines with this goal in mind. Frankly, verification is a job for the talk page, not the article.

What I would recommend is to simply give three Harvard references. Since we are using the {{citation}} template we can get automatic links from references to citations, like so:

"since it makes all three equations valid (Lay 2005; Meyer 2001; Strang 2005)."
markup: "since it makes all three equations valid ({{harvnb|Lay|2005}}; {{harvnb|Meyer|2001}}; {{harvnb|Strang|2005}})."
  • Lay, David C. (August 22, 2005), Linear Algebra and Its Applications (3rd ed.), Addison Wesley, ISBN 978-0321287137 
  • Meyer, Carl D. (February 15, 2001), Matrix Analysis and Applied Linear Algebra, Society for Industrial and Applied Mathematics (SIAM), ISBN 978-0898714548 
  • Strang, Gilbert (July 19, 2005), Linear Algebra and Its Applications (4th ed.), Brooks Cole, ISBN 978-0030105678 

If you'd like to see a more extended example, visit Area of a disk, one of our A-rated mathematics articles. --KSmrqT 18:21, 12 September 2007 (UTC)

[edit] Note on images

Thank you for the very nice Image:Inverse Function.png and many other pictures you added. I have a comment. I think it is good if you upload the pictures directly to commons, as there they can be used by other projects. Also, is it possible to upload the pictures in SVG format, or otherwise submit the source code to them? That can be great resource if the pictures need to be edited in the future, or to help generate similar pictures for other needs. Wonder what you think. Thanks. You can reply here. Oleg Alexandrov (talk) 15:19, 19 September 2007 (UTC)

First, I'd like to thank you for being so generally supportive of me as a new editor. You and Jitse have contributed a lot to making me feel welcome here at Wikipedia.
I'd be happy to download pictures to the commons instead of here. As for the SVG format, I've been making most of my pictures using Microsoft Word (the 3D picture on linking number being an exception), which uses the native Windows vector graphics format (WMF). There exist tools for converting WMF to SVG, and as soon as I get one working I'll be able to go through and change the format of all my old pictures. (In the long run, I should probably just switch to using Inkscape.)
By the way, do you know anything about which fonts I should be using? For example, do you know whether Arial or Computer Modern are copyrighted? If so, do I need to switch to some alternative public-domain fonts? Jim 16:11, 19 September 2007 (UTC)
I am surprised Word can draw such nice pictures. About fonts, I don't really know. I would doubt though that the font making companies would care if you use their copyrighted fonts in diagrams, I would assume that the fonts are copyrighted primarily to prevent other font companies from using them or modifying, rather than the end user. But I am not a lawyer. :) Cheers, Oleg Alexandrov (talk) 21:52, 19 September 2007 (UTC)
Oleg, I've figured out how to change to SVG, and I've replaced the images from the linking number page. I'll be converting the rest of my images over the course of the next week. Jim 20:47, 20 September 2007 (UTC)
The list of fonts (typefaces) available for use in SVG files to be rendered by MediaWiki (using librsvg) is provided at m:SVG fonts. All of them are freely available for download, so you can install them on your own machine to preview results. Other fonts, even those in the public domain, are not supported. However, if you really, really must have a particular glyph not found in any of these fonts, convert its outline to a path; you'll lose the rasterizing hints but retain the shape. --KSmrqT 23:23, 20 September 2007 (UTC)
Thanks! Jim 23:50, 20 September 2007 (UTC)

[edit] Back to work

Thanks a lot for your kinds words. Yes, I agree, I guess you are smart, stubborn and constructive as well as I am, and a good mathematician, but we use our mind in different ways. We will probably be able to do a good job together, and with the help of KSmrq, which is one of the best writers in Wikipedia:WikiProject Mathematics, in my opinion! And I hope others will participate in the discussion Paolo.dL 21:12, 21 September 2007 (UTC)

Now, I will try again to show you are wrong. Please don't be offended. It is not intended to be a personal attack. It is just the best way I can find to accomplish our common objective: improving the article about inverse function. I will be happy if you can prove that you are right this time as well ;-) But be careful, this time if you show you are right, I will be able to show that you were not clear enough in the article! :-)

[edit] Request for picture

Hi Jim. I was thinking that it would be nice if the article Fixed point (mathematics) had a picture at the top illustrating the concept of a fixed point. I think the picture Image:Inverse Function Graph.png you made could be easily adapted to that, by just removing one of the two curves and maybe emphasizing the intersections of the graph with y=x. I'd do it myself, but that figure is available only in PNG. So, I wonder, could you generate the above modification and post a new picture at the fixed point article? That would be very much appreciated. Thanks! Oleg Alexandrov (talk) 23:01, 21 September 2007 (UTC)

Oleg, I added the picture to fixed point (mathematics). I haven't figured out yet how to have text in SVGs, but as soon as I do I'll replace it with an SVG and upload it to the Commons. Jim 23:45, 21 September 2007 (UTC)
Thanks, that was quick! By the way, you can upload PNG images to commons too. I just migrated Image:Fixed Point Graph.png to there (so, if you visit the image, you will see that the page is red, but the commons image is transcluded on it).
By the way, I wonder if in the picture things would look better if the graph of the function is in blue, while the fixed points are in red. Somehow I think the fixed points should be in a brigher color since they are what matters in the figure. But everybody has different taste for color schemes, so please treat this just as a particular observation. I am very grateful for you making this nice picture. Oleg Alexandrov (talk) 00:13, 22 September 2007 (UTC)
I tried red but for some reason it didn't look very good. What do you think of this? Jim 00:37, 22 September 2007 (UTC)
That's great, thanks! Oleg Alexandrov (talk) 00:48, 22 September 2007 (UTC)
Happy to help. :-) Jim 00:52, 22 September 2007 (UTC)
As Oleg says, our illustrators use a variety of color schemes. My figures are easy to recognize by the four colors I regularly use: red, green, blue, and yellow. Ah, but I use highly specific ones, taken from research relating to the opponent process in human color vision (and linguistic research on color names). I keep a display on my user page for easy reference:
♦Black:  #000000 = RGB(  0,   0,   0)
♦White:  #ffffff = RGB(255, 255, 255)
♦Red:    #bc1e47 = RGB(188,  30,  71)
♦Green:  #009246 = RGB(  0, 146,  70)
♦Blue:   #0081cd = RGB(  0, 129, 205)
♦Yellow: #fec200 = RGB(254, 194,   0)
For a gray, I sometimes use "#b3b3b3", RGB(179,179,179).

--KSmrqT 01:19, 23 September 2007 (UTC)

That's awesome! You should consider posting this somewhere public, i.e. Wikipedia:How to create graphs for Wikipedia articles. Jim 01:29, 23 September 2007 (UTC)

[edit] Unreported arbitrary deletions

Jim, you deleted again without warning and without explanation! This is too (twice) bad. And you deleted a paragraph which was already restored after your first unreported deletion! I motivated that restoration in the talk page, and you totally ignored my contribution. Moreover, I already complained on the talk page about your many unreported, distructive and questionable deletions. Your behaviour is unacceptable. Please:

  1. always discuss each important edit (and deletion) in the talk page,
  2. don't ever revert a previous motivated edit without warning and explanation, and
  3. whenever possible, edit section by section (that's by far the best solution), using the specific edit link that you can find on the right of each section title.

Thanks, Paolo.dL 10:34, 22 September 2007 (UTC)

Paolo, see my response on the talk page. I think you are misinterpreting Wikipedia custom. Are there any Wikipedia guidelines to support your requests above? Jim 16:37, 22 September 2007 (UTC)
I'm happy to honor some of these requests, though. For example, I'm happy to edit section by section if that would help (though this isn't possible for edits that reorganize the sections). In any case, I think I've figured out the edit that annoyed you (the text on notation that you reinserted), and I think you don't realize that I moved this text to the end of the previous subsection. See my comment on the talk page at the end of "First step". Jim 17:06, 22 September 2007 (UTC)

I am sorry to read that you are tired of the discussion. You gave a great contribution. I hope you will change your mind and come back. I was upset because you did a second extensive edit for which, again, I couldn't understand the details because it was too extensive and not well documented (this is why I mistook your move for a deletion). The comparison in the history page is useless in this case. However, don't worry, your explanations will be taken into account with maximum respect. Your latest comment is enlightening. I hope that you are right, and that only two very similar definitions exist, because the version by Norwood seems to be too complex.

By the way, have you seen the 19 September comment by KSmrq on Talk:function (mathematics)? He also seems to say that someone defines inverse of f as a function g such that f( g(y) ) = y, and that's bad news, because I can't understand the rationale of this third definition. Paolo.dL 00:38, 23 September 2007 (UTC)

Paolo, thank you for the fine discussion. I really do want to move on: this article has been taking up all of my Wikipedia time, and I'd rather work on other things. (I just posted an article on geometric series, I'd like to help improve free group and dihedral group, and I'd like to do something about plane (mathematics).) I'm sure you and KSmrq will make a good team.
Cheers, Jim 01:18, 23 September 2007 (UTC)
I don't think that's going to happen. Paolo is neither mathematically advanced, nor a native speaker, nor adept with Wikipedia conventions and etiquette. You, Jim, have been very patient in dealing with him and improving the article. I don't have the patience and interest to do so, especially if you are moving on to other pursuits. I've revised the opening, said a few words about it on the talk page, and will probably leave it at that. --KSmrqT 01:35, 23 September 2007 (UTC)

[edit] Free group

As I see it, there is no problem with this article, except for topics that could be added. So, unless you have some new information to add, I suggest that it's not a great idea to change it according to your own model. This is not how WP works. You seem to want to restyle this page. I'm not sure that's a good idea, because in mathematics content is far more important. Please concentrate on that. Personally, I just add to WP pages when I look something up and find a neglected article, like the graph of groups article that I worked on with Serre by my side (the book, not the person :)). There are missing topics and it's those we should concentrate on. Mathsci 18:48, 23 September 2007 (UTC)

I don't know. I think the article could use a lot more explanation that's accessible to non-group theorists. Free groups are quite important, and it seems to me that the article should be much longer and more thorough than it is. Particularly missing is a longer discussion of the relationship to presentations, a detailed description of the connection with topology, a coherent description of the Cayley graph, and so forth.
If you don't agree, though, I'm happy to leave the article alone for now. I'm relatively new to Wikipedia, so it's quite possible that I'm misjudging what should be in an article like this. I'll come back and take a look at the article again after I have some more experience. Jim 19:07, 23 September 2007 (UTC)

[edit] Geometric series

Hey, nice work on Geometric series. I wished we had an article there before, but I never did go to the trouble of writing it, so I'm glad you did! Melchoir 23:24, 23 September 2007 (UTC)

I'm glad you like the article! :-) Jim 23:26, 23 September 2007 (UTC)

[edit] FYI: Function (mathematics)

I have just completely replaced the inverse function section of the Function article with an extended example. Logically it might better reside in the Inverse function article, but Paolo had turned the section into a mathematical and linguistic disaster. You might find it of interest; it combines algebra with geometry in a way I hope readers will find understandable and engaging. (I think it is not common knowledge that every cubic Bézier curve has a rational linear inverse that gives the parameter value for each point on the curve, excepting double points.)

Given that Paolo is weak in both English and mathematics, it baffles me why he insists on trying to "help" us explain mathematics more clearly. He seems to mean well, but that's no substitute for expertise or wisdom. (I should also warn you about Melchoir, but I'm not sure where to begin.) Ah, the joys of "anyone can edit"! --KSmrqT 10:03, 28 September 2007 (UTC)

Looks good! You might want to mention that invertible functions are one-to-one—you develop this idea in the second paragraph, but you never name it explicitly.
By the way, I really like the "Fahrenheit to Celsius" example that you've put in both articles. It's wonderfully concrete, and captures the idea of inverse function much better than clear language ever could. I'll definitely use it the next time I teach calculus. Jim 16:59, 28 September 2007 (UTC)
Thanks. One risk of that example is that readers in the US will say "What's Celsius?", and readers everywhere else will say "What's Fahrenheit?" Still, the benefit is worth the risk. It's funny how well the mind responds to concrete examples. I've read that students can quickly solve problems expressed as a money calculation, yet be baffled by the same problems as pure numbers.
I cringe from the "one-to-one" language, because I learned three easily-confused expressions. The "onto" part was never a problem, but we have "one-to-one", "one-one", and "one-to-one correspondence". I find it easy to remember that "epi" is the Greek equivalent of "on", as "sur" is the French equivalent; so injection/surjection/bijection and monomorphism/epimorphism/isomorphism work well in my mind. The "-jections" are particularly graphic for me, and have nice "-jective" forms as well.
But now user Wvbailey (talk · contribs) comes and ravages the "Definition" section of Function. If you like mathematics and if you like good writing, it can be painful to look at articles that are too popular; they regularly get "improved" into incorrect, unstructured eyesores. I contribute to basic articles sporadically as a public service; more than that and I'd burn out. --KSmrqT 20:29, 28 September 2007 (UTC)
One-to-one
I suppose I prefer injection/surjection/bijection as well, at least in the context of talking with other mathematicians. It's amazing how many different words mathematicians have for these concepts, all with slightly different meanings:
  • Function, mapping, map, transformation, assignment, labeling, operator, functional, correspondence, morphism
  • Injection, one-to-one, inclusion, monomorphism, embedding
  • Surjection, onto, epimorphism, covering, quotient map, projection
  • Bijection, correspondence, one-to-one correspondence, isomorphism, pairing, identification
Though many of these have specific definitions, I can imagine using any of them in a wide variety of contexts. For example, "covering" usually refers to a specific kind of map between topological spaces, but I know that I've used the word in entirely non-topological settings (e.g. to invoke a certain image when describing the quotient map Z → Z/nZ).
My impression is that calculus and precalculus books (in the United States, at least) use the "one-to-one" terminology exclusively for injections. I can understand this choice—the phrase is simple and descriptive enough to be non-threatening for high-school students. The result is that articles on Wikipedia that wish to be accessible to high-school students (and others who haven't studied advanced mathematics) are probably better off using "one-to-one".
Basic articles
As for the article on functions, I agree that Wvbailey's edits seem generally unhelpful. I don't really understand yet the procedure by which articles on Wikipedia become better over time. Can this kind of thing happen to FA-quality articles? How would the current function (mathematics) article get from its current state to a state where it is both well-written and relatively stable? Jim 22:48, 28 September 2007 (UTC)
Articles do not improve monotonically. Highly visible mathematics articles like Geometry are regularly vandalized, with some kid inserting a sentence like "My geometry teacher is gay." We can easily spot and revert most of this, but it discourages good editors from working on the target. Another level of vandalism deliberately inserts false claims and mistakes. More difficult still, people "correct" things they do not understand, breaking them in the process. Errors that only an expert will spot can persist uncomfortably long.
Nevertheless, articles can improve, sometimes dramatically. Optimistically, the process is like simulated annealing: some changes make an article worse, but we hope the overall trend is positive. Small steps are often corrections of spelling or grammar or calculations. Some are markup or formatting improvements. Major or minor collaborations can occur, either organized or accidentally, as recently happened with Integral. Or an editor can act as a "champion", writing or significantly overhauling an article alone. (This is risky; no doubt Wvbailey thought that is what he was doing at Function.)
What are the chances an editor is familiar with serious mathematics? Can write for the expert as well as for the layman and the young, all in the same article? Properly employs grammar, spelling, and punctuation, and writes clear, concise, well-structured, and engaging English prose? Has mastered the labyrinth of wiki mathematics markup? Can cope with the exasperations of wiki politics? Has time and an inclination to donate those talents without recognition or permanence?
Were someone to propose a project like this the rational response would be, "You're nuts; that could never work." Yet for all Wikipedia's problems, it is a remarkable achievement. I don't have an explanation, but I believe a nebulous concept called "community" is a factor. Still, I believe almost any major improvement can traced to a champion, somebody like you who sees a problem and decides to do something about it. --KSmrqT 06:16, 29 September 2007 (UTC)

[edit] Homotopy groups of spheres

Many thanks for the offer of help. Basically, FAC is a process which assesses an article against the featured article criteria and passes the article if it meets these criteria. Ideally, everyone involved should be working towards a common goal, but in practise there are usually two camps: those giving reasons why the article does not meet the criteria, and those trying to fix the article so that it does.

But, before we go there, what do you think of the article at the moment? Geometry guy 20:05, 7 October 2007 (UTC)

After looking at the article, I understand why you think this would be a good FA candidate. In its current state, this article is far better than most mathematics articles, including related articles such as topology, algebraic topology, homotopy, and homotopy group. In particular, I think the article does an excellent job of being as accessible as possible to non-mathematicians.
If I had to identify one weakness of the article, I would suggest that the explanations of the low-dimensional examples could use some expansion, and possibly some more pictures. I'm not sure whether this is the kind of suggestion you're looking for—are we trying to improve the article in general, or should we focus more on things like clarifying the prose and expanding the references?
In any case, I can offer the following sorts of help:
  1. General suggestions for improving/expanding the article.
  2. Specific suggestions for improving clarity and wording.
  3. More or improved pictures (see my picture gallery).
Jim 22:41, 7 October 2007 (UTC)
Good suggestions and I am very much in favour of improving the article in general. Some more pictures would be great, and all the help you offer would be much appreciated. Geometry guy 09:09, 8 October 2007 (UTC)

Hi again Jim. I was wondering if you could track down a reference for the application of homotopy groups of spheres to critical points (in singularity theory I guess). Geometry guy 12:46, 21 October 2007 (UTC)

It's hard to give a specific reference—I've sort of summarized a whole class of common constructions. The idea is most commonly applied to πn(Sn), e.g. in the definition of the index of an isolated zero of a vector field, or in the definition of the ramification index for a map between Riemann surfaces. An expert in differential topology or algebraic geometry might know a good general reference. Jim 07:50, 24 October 2007 (UTC)

[edit] Information about vector images creation

Hi.

My name is Peleg, and I am an Israeli Wikipedian (living in London). I program a lot, and just now I met the GD library of PHP, and started creating some vector images.

I have seen your beautiful work:

And I would like to create such images for MANY other Wikipedian and Wikibooks articles that lack these wonderful illustration of vector spaces, functions, etc.

If you could only give me a start, a hint about where to study how to do this (is it possible to learn it by yourself quickly?) I would be greatful; I have time to invest in it, and I can contribute it to Wikipedia, but as I think about life itself: it's better to contribute by doing things that you LOVE, and I believe that I'll love doing that.

Thanks ahead, Peleg 10:17, 9 November 2007 (UTC)

That's a hard question to answer. I've been making mathematical pictures for several years as part of my job, and I've recently made several dozen for Wikipedia (see my image gallery). The picture above was made entirely using the drawing tools in Microsoft Word, but sometimes I also use Inkscape for vector graphics, and POV-Ray for three-dimensional rendering. Other popular vector graphics programs include Xfig and Adobe Illustrator.
The picture above is drawn in perspective, with the top of the picture being the horizon. Perspective drawing is covered in most basic art books, or (if you are more mathematically inclined) in most treatments of projective geometry. The idea is that parallel lines should meet at the same spot on the horizon— in the picture above, all of the diagonal lines meet at the upper-right corner of the drawing. Since I didn't want to have to draw more than about 30 lines myself, I added a transparency gradient near the top of the drawing to create the "mist" near the horizon.
By the way, I made this drawing a while ago when I was first experimenting with 3D, and if I had to do it over I would use POV-Ray. This is a 3D program with an input language similar to C, and it calculates the perspective and everything automatically. I learned how to use POV-Ray entirely from the tutorial and help that comes with the program.
Here are some general tips for making images in Wikipedia:
Well, I've tried to cover all the bases. I could probably be more helpful if you could give some details on what kinds of pictures you're thinking of making, and which parts of picture-making you'd like to talk about. Jim (talk) 07:42, 22 January 2008 (UTC)
Hey - thanks!
I am currently on a "WikiBreak" myslef (more like a LifeBreak :-) ) due to exam season in my university (math).
I hope that I'll be back in business soon, and if I'll have more specific questions, I'll ask you...
Thanks! Peleg (talk) 00:24, 25 January 2008 (UTC)

[edit] Arrangement of hyperplanes etc

Hi I just read your post on my talk page (I don't look at it very often as you can see). The illustrations are very easy to do, but you'd have to explain the concept in terms that a 3D animator can understand. Let me know.

[edit] Your Draft on Representation Theory of the Dihedral Group

Hello! Just glancing at your character table for D5, and I know it cannot be quite right. For example, if you do the inner product of the 1/5-representation with itself, you ought to get 1, and you do not. For presumably correct tables, see http://mathworld.wolfram.com/CharacterTable.html Anyway, just thought I'd pass that on... this draft seems like it could potentially make a good article! Kier07 (talk) 23:45, 29 February 2008 (UTC)