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• CommentAuthorKevin Lin
• CommentTimeDec 26th 2009 edited

Perhaps it will be impossible to come to a consensus about this, but I'd like to know what people's preferences are as to using infinity vs. $\infty$ vs. oo vs. ∞ when talking about (infinity,n)-categories and the like. It's relevant because I'd ideally like to be able to find questions/answers that mention (infinity,n)-categories without having to do a couple separate searches. People might also have other considerations regarding this choice that I haven't thought of.

You might say that having a [higher-category-theory] tag makes this largely-irrelevant issue even more irrelevant but sometimes (infinity,n)-categories come up even when the question isn't directly about them, e.g. http://mathoverflow.net/questions/2185/how-to-think-about-model-categories or http://mathoverflow.net/questions/5236/abstract-relation-between-presehaves-and-simplicial-sets

I also wonder if there is a consensus about this on the nLab? I am not an active nLab member, but maybe someone else here is and knows?

Sorry if I'm being pedantic.

1.

With the disclaimer that this is just my opinion, I think the title should be in plain (spoken) English and the text should say $(\infty, n)$ or (∞, n) as it's a standard notation. oo should be discouraged.

Note that ∞-categories seems to be a standard notation for what others call (∞, 1)-categories, so the search by notation won't be trivial. In my opinion, you're better off aggregating several tags, especially [ct.category-theory] and finding out the questions you need manually from that list.

2.

I agree with Ilya that it should be $(\infty, n)$, (infinity, n), or (∞, n), but not (oo,n).

3.
As the offending party, my reasoning was that it looks nicer in the topic title to put (oo,n), but in the question text, I always use "$(\infty ,n)$-category". I didn't know what the unicode for it was, but it would be nice if on the sidebar there was a reference for the unicode for commonly used mathematical symbols like infinity, if only for topic titles.
• CommentAuthorrwbarton
• CommentTimeDec 26th 2009

You can just use the HTML entity &infin; rather than the numeric Unicode value. However my recollection is that neither of these work in titles and you have to type symbols directly somehow (I usually copy and paste from Wikipedia).
4.

Is this a bug, btw, the titles don't allow many Unicode characters (or rather render them badly)? I notced Greg's first question was messed up by this.

5.

Titles escape the ampersand — which isn't the best idea, imho.

@Harry, I would do ∞-categories in the title in this particular case.

• CommentAuthorKevin Lin
• CommentTimeDec 26th 2009

Harry: Naw, you're not the "offending party"; I mean I tried out "oo" in a recent post too. And I've noticed that Urs Schreiber and various other n-category-cafe people seem like to use "oo" as well.

• CommentAuthorKevin Lin
• CommentTimeDec 26th 2009

What's the advantage of unicode and HTML entities over LaTeX? Is it that the former is somehow a more standardized, universal, more-likely-to-be-around-in-50-years kind of thing?

• CommentAuthorHarry Gindi
• CommentTimeDec 26th 2009 edited

@Kevin: They don't require jsmath rendering and also work in the titles.

@Ilya: How the heck did you just do that if not by html, unicode, or copy/paste?
6.

I did copy/paste, but now you can do that too :)

• CommentAuthorHarry Gindi
• CommentTimeDec 26th 2009 edited

Can we put that character on the sidebar for those of us who are too lazy to map the character to our keyboards?
7.
On the nLab we almost always use TeX $\infty$. That doesn't work in page titles or hyperlinks, though, so page titles are written in English, but usually with redirects that use Unicode, so that we can type [[∞-category]] to make a nice-looking link. There's been some discussion of whether this should be the other way 'round, but that's the way it is at the moment.

Regarding typing Unicode, there is something called SCIM, but I haven't managed to get it to work myself. What I use is that in Emacs, you can hit Ctrl-\ and type "tex" when prompted for an input method, after which you can simply type "\infty" and the Unicode character ∞ will come out. And the Firefox plugin "itsalltext" is convenient for editing textareas in an external editor (like Emacs).