## Contributing to Wikipedia

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Well, I decided to write my first Wikipedia article, which is on the Lie group $\mbox{SL}_2(\mathbb{R})$. I look up mathematics on Wikipedia a lot, and I’ve also been linking to Wikipedia articles in my blog entries, so I thought I should start giving back.

I’m not a particular expert on $\mbox{SL}_2(\mathbb{R})$, and I wrote the article mainly because I wanted to include the classification of elements into elliptic, parabolic, and hyperbolic, as groundwork for writing articles on isometries of the hyperbolic plane and on the classification of self-homeomorphisms of the torus.

Please let me know if you have any comments or suggestions. If anyone would be willing to help, it could use a better summary of the representation theory (although there is also a whole article on that subject), and could also probably use a section entitled “algebraic structure”. In addition, I wasn’t really confident enough with my algebraic geometry to write anything about the relationship with moduli space.

### 4 Responses to “Contributing to Wikipedia”

1. Blake Stacey Says:

Looks like a good beginning!

One thing which die-hard Wikipedians like is “inline citation,” which typically implies footnotes throughout the text. Math topics may not lend themselves naturally to this treatment; one expects that several books say roughly the same things about $SL_2(\mathbb{R})$ at the same level, and citing on a sentence-by-sentence basis would seem kind of foolish. Still, if certain sources have, in your judgment, better treatments of particular aspects, it might be nice to footnote appropriately.

2. John Armstrong Says:

Inline citation and footnoting is good, to a point. If the pendulum starts to swing the other way, I will fight unto my dying breath to prevent mathematics from succumbing to Bluebooking. We’re horrible enough at teaching graduate students how to be mathematicians (getting papers published, speaking invitations, grants, jobs…) that to add more requirements will be the death-knell.

3. Some Wikipedian Says:

There are specific guidelines for citation in mathematics and many scientific disciplines, which developed through consensus for the very reasons discussed in the other comments.

I recommend looking over http://en.wikipedia.org/wiki/Wikipedia:WikiProject_Mathematics

especially the discussions that go on their on the talk page. Almost every kind of issue with writing mathematics on Wikipedia has been extensively discussed here.

4. Jim Belk Says:

Thanks for the links — they make useful bookmarks.

On the subject of footnotes, I wholeheartedly agree that Wikipedia articles are better when they have citations. Unfortunately, I don’t really know any good sources on the subject at hand. I put a link to Lang’s $\mathrm{SL}_2(\mathbb{R})$ book (which I have not read, but is almost certainly relevant), and I copied a few references from the “representation theory of $\mathrm{SL}_2$ article.

I suppose I should hope that someone else comes along and adds some references to the article. (At the same time, I should probably pay more attention in the future to whether math articles I’m reading could use more citations.) Alternatively, I could add an “article with unsourced statements” tag to the top of the article, but I’m not sure whether the problem is serious enough to warrant it.

By the way, here’s a random question: Is there any way to search the various help pages and project pages in Wikipedia? They don’t seem to appear when you do a Wikipedia search. I know I could do a site search with google, but there ought to be something better.