## August 16, 2006

### Inaugural Post

#### Posted by Distler

Welcome to John Baez, David Corfield and Urs Schreiber. Their brand-new blog, The n-Category Café, will focus on that heady interface between Physics, Mathematics and Philosophy.

Posted at August 16, 2006 6:41 PM UTC

TrackBack URL for this Entry:   http://golem.ph.utexas.edu/cgi-bin/MT-3.0/dxy-tb.fcgi/889

Read the post The n-Category Café
Weblog: The String Coffee Table
Excerpt: New group blog: "The n-Category Cafe".
Tracked: August 17, 2006 12:26 PM

### Re: Inaugural Post

Welcome guys! Sounds like a lot of fun - I look forward to your posts. Cheers.

Posted by: Mark Trodden on August 17, 2006 2:04 PM | Permalink | Reply to this
Read the post The Physics Group Blog Bug is Contagious
Weblog: Cosmic Variance
Excerpt: Jacques is advertising the launch of a new physics group blog - the n-Category Café. Run by John Baez, David Corfield and Urs Schreiber ( of the String Coffee Table), with technical support from Jacques himself. Their self-described brief is the inte...
Tracked: August 17, 2006 2:07 PM

### Re: Inaugural Post

Fantastic!

What a great place to visit every day!

Best wishes,
Christine

Posted by: Christine Dantas on August 17, 2006 3:32 PM | Permalink | Reply to this

### Re: Inaugural Post

Every day? Thanks! But it will take us a while to get up to speed. David is on vacation with family in France until September, and tomorrow I’m going to Suzhou for three days - a little sidetrip from Shanghai.

Even when we get rolling, our blog may be a bit on the dry side. For example, one reason we started it is to have a better forum for discussing Klein 2-geometry. But, we’ll try to provide at least a little fun. And who knows - Urs may turn out to have a wild and crazy side we’d never suspected.

Posted by: John Baez on August 17, 2006 4:48 PM | Permalink | Reply to this

### Re: Inaugural Post

Message acknowledged. Perhaps I have exaggerated. I was thrilled to see your new blog then jumped to write something that reflected my enthusiasm. In any case do not worry, I’ll be patient. And I also get fun with dry contents.
Have a nice trip,
Christine

Posted by: Christine Dantas on August 17, 2006 5:12 PM | Permalink | Reply to this

### Re: Inaugural Post

Posted by: Aaron Bergman on August 17, 2006 5:29 PM | Permalink | Reply to this

### Re: Inaugural Post

Are you volunteering? ;)

With all the bigshots roaming in toposes undreamt of, somebody has to pick up the pebbles that will constitute 22nd century school books.

So, take some elementary book, say on basic group theory. Categorify everything in sight.

Maybe surprisingly, for instance already the mere concept of a sub-2-group requires serious thought - if done properly.

So it’s very good that somebody is looking into that. Where were we if we didn’t know what a sub-1-groups are, simply because everybody was already gone studying generalized twisted formal quantum groups internalized into the topos of transrational numbers?

For instance: what is the intrinsic notion of having a nonabelian gerbe with reducible structure 2-group?

I’ll wait for John and David to figure out Klein-2-geometry before trying to think about that one.

Posted by: urs on August 17, 2006 5:46 PM | Permalink | Reply to this

### Klein Geometry

Just in case it is not clear to anyone reading this: Klein 2-geometry is supposed to be the categorification of
Klein Geometry.

Posted by: urs on August 17, 2006 6:06 PM | Permalink | Reply to this

### Fun

Even when we get rolling, our blog may be a bit on the dry side. For example, one reason we started it is to have a better forum for discussing Klein 2-geometry. But, we’ll try to provide at least a little fun.

Is there anything more fun than a technical discussion of 2-geometry?

I can’t think of anything.

Seriously, though, I think the commutative diagrams that crop up in (n-)Category Theory will push the typesetting abilities of itex to the limit.

I wish there were a practical way to mix SVG and MathML. Then one could do an itex version of DCpic.sty, which is the categorification of LaTeX. That’s what one really wants to use here…

Posted by: Jacques Distler on August 17, 2006 5:32 PM | Permalink | PGP Sig | Reply to this

### itex diagrams

I wish there were […]

That would be awesome.

Unfortunately, I don’t have any clue what needed to be done. Would there be any point is, say, contacting the two guys who wrote xypic, seeing if they can turn it into something that could be used for web publishing.

(You see, I don’t know what I am talking about… ;-)

Posted by: urs on August 17, 2006 5:52 PM | Permalink | Reply to this

### Re: itex diagrams

Would there be any point is, say, contacting the two guys who wrote xypic, seeing if they can turn it into something that could be used for web publishing.

No. The problem is not on the input side. The problem is on the output side. The kind of fancy diagrams produced by DCpic.sty (or XYpic.sty) are beyond the territory of MathML. One really needs to use SVG. Or, more properly, one wants to be able to freely mix MathML and SVG.

The kind of compound documents one wants to be able to create are currently not possible.

(There’s also the small problem of writing a converter from DCpic.sty syntax to this hypothetical mixture of MathML and SVG — a task well-beyond my modest programming abilities. But that’s probably fixable.)

Posted by: Jacques Distler on August 17, 2006 6:05 PM | Permalink | PGP Sig | Reply to this

### Re: Fun

Since the SVG thread is going here:

What would be really cool is if you could mix SVG and MathML and then convert it to .pdf, so I could make one figure for both my talks (in xhtml) and my papers (since I doubt Phys. Rev. is going to accept antything other than .pdf). Apache FOP is a step in the right direction, but it’s a real pain in the !\$@.

Posted by: A on August 18, 2006 2:31 AM | Permalink | Reply to this

### SVG

No one (no human, anyway) authors MathML and SVG “by hand.”

I use Adobe Illustrator to prepare figures. It can output to EPS and PDF (for papers) and to SVG and GIF (for the web).

One can place mathematical text (generated, say, using TeX and dvips) in the figures, with no problem at all. That works fine in the EPS and PDF versions of the figure.

Unfortunately, embedding fonts in an SVG figure is nearly useless, as I have discovered. For portability, one really needs to convert the fonts to outlines, when saving to SVG.

Other than that, it’s great to be able to be able to output the same figure in these different formats for use in papers and on the web.

Posted by: Jacques Distler on August 18, 2006 3:07 AM | Permalink | PGP Sig | Reply to this

### Re: Inaugural Post

I suppose this makes Jacques a functor?

Posted by: Garrett on August 17, 2006 4:49 PM | Permalink | Reply to this

### Re: Inaugural Post

Glad you guys have started this; I’m really looking forward to it.

John, is there an RSS feed available for This Week’s Finds in Mathematical Physics? If not, any chance you could be convinced to add one?

Posted by: David Carlton on August 17, 2006 5:11 PM | Permalink | Reply to this

### Re: Inaugural Post

Posted by: Boris on August 17, 2006 6:13 PM | Permalink | Reply to this
Weblog: The n-Category Café
Excerpt: Discussion of n-category description of supergravity continued.
Tracked: August 17, 2006 7:53 PM
Weblog: Life on the Lattice
Excerpt: There is a new group blog in town: over at Jacques Distler's golem, arch-proto-blogger John Baez, String Coffe Table-host Urs Schreiber and philosopher of mathematics David Corfield have formed the n-Category Café, where they will discuss the mathem...
Tracked: August 17, 2006 9:37 PM

### Re: Inaugural Post

This looks like fun! I’m rather excited about this blog. I’m a big fan of “This weeks finds…”, it’s helped me immensely with my Ma thesis (especially the parts on triality of SO(8) and the octonions).

-Dimi

Posted by: Dimitri Terryn on August 17, 2006 10:16 PM | Permalink | Reply to this

### LOVELY!!!

JB, as I told you over at physicsforums, even as a beginning undergraduate your lecture on higher dimensional algebras has had an affect on me and makes me want to think as category theoretic as possible. Ie, I’m positively thrilled this blog exists. Thanks folks :)

Posted by: duke_nemmerle on August 19, 2006 6:00 PM | Permalink | Reply to this

### Good Luck

It is good to see what looks like a focused research blog, it will be interesting to keep an eye and see how it goes. Good luck guys with this experiment, may your blog stay dry!

Posted by: Moshe on August 20, 2006 3:45 AM | Permalink | Reply to this
Read the post Toward a Higher-Dimensional Wiki
Weblog: The n-Category Café
Excerpt: Let's talk about setting up a wiki for n-category theory and other aspects of higher-dimensional algebra!
Tracked: September 2, 2007 1:32 PM

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