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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeSep 3rd 2010
• (edited Sep 3rd 2010)

to my surprise I notice that with current nominal count of 3930 nLab entries we are quite close to number 4001. So maybe, to establish a tradition we might want to post a followup to 3000 and One Things to Think About but in the style of David Corfield’s nLab Digest last time (see there to get an impression for what I mean).

So, I invite everyone to post here within the next weeks a little blurb in this style, if desired, which we can then all collect together into a blog post.

• CommentRowNumber2.
• CommentAuthorTobyBartels
• CommentTimeSep 3rd 2010

Corrected link:

nLab Digest

• CommentRowNumber3.
• CommentAuthorUrs
• CommentTimeSep 3rd 2010

Thanks. Fixed.

• CommentRowNumber4.
• CommentAuthorzskoda
• CommentTimeSep 16th 2010
• (edited Sep 16th 2010)

It seems we are all too busy to prepare a digest right now. The announcement was 13 days ago when the count was 3930; nobody had time to write his "report"; maybe we should postpone it to some other moment (when is 2 years of nlab ?).

Today the count is 4045, that is, we produced 115 new stubs in main nlab web after 13 days. That is, we could have 4500 by early or mid November and 5000 early in the new year. Or maybe few days before the New Year...who knows.

• CommentRowNumber5.
• CommentAuthorzskoda
• CommentTimeSep 16th 2010
• (edited Sep 16th 2010)

November 28, 2008 02:18:19, according to http://ncatlab.org/nlab/revision/HomePage/1. Edit: the first entry of nlab. So nlab is 2 on November 28, 2010.

• CommentRowNumber6.
• CommentAuthorzskoda
• CommentTimeOct 27th 2010
• (edited Oct 27th 2010)

Tomorrow is the 2nd birthday of the $n$lab! What about announcing it, at least, on the cafe ?

By the way: somebody put induced topology in nlabmeta: induced topology (nlabmeta). It looks wrong to me.

• CommentRowNumber7.
• CommentAuthorTim_Porter
• CommentTimeOct 27th 2010
• (edited Oct 27th 2010)

@Zoran. It is still October! You had me worried for a moment. :-)

Your idea of doing a post on the Café for the 2nd birthday (in a month’s time) is a good one.

• CommentRowNumber8.
• CommentAuthorzskoda
• CommentTimeOct 27th 2010

oh good!

• CommentRowNumber9.
• CommentAuthorDavidRoberts
• CommentTimeOct 28th 2010

I think the definition is right, but too complicated. Really one should say the induced topology is the smallest topology on the set $X$ such that all the maps $f_i:X \to X_i$ are continuous. This is just a expanded application of it. I’m not sure why Vishal put it on nLab meta, rather than the real nLab…

• CommentRowNumber10.
• CommentAuthorUrs
• CommentTimeOct 28th 2010
• (edited Oct 28th 2010)

I’m not sure why Vishal put it on nLab meta, rather than the real nLab…

Like, by accident?

Let’s discuss it thoroughly. Maybe eventually a lab elf comes and moves it over to the nlab.

• CommentRowNumber11.
• CommentAuthorTodd_Trimble
• CommentTimeOct 28th 2010

I don’t think there’s much to discuss; I advised him to put it on the nLab, and he probably meant to but got sidetracked. I’ll point Vishal here and let him decide, or I can move it.

• CommentRowNumber12.
• CommentAuthorDavidRoberts
• CommentTimeOct 28th 2010

This is just a expanded application of it.

actually I’ve decided it’s a good explanation: it shows that there is such a smallest topology. The unsaturated links just clog the page up a little.

We should (i.e. I shouldn’t be lazy) also put a page for the dual: the induced topology on a set $X$ given a bunch of maps $f_{ij}:X_i \to X$ is the largest topology such that all the $f_{ij}$ are continuous. For example, this is how the kelleyfication is defined in Ronnie Brown’s book: take $X_i$ to be all compact Hausdorff spaces, $X$ a space and $f_{ij}$ all continuous maps.

•
• CommentRowNumber13.
• CommentAuthorvishallama
• CommentTimeOct 28th 2010
Sorry everyone for posting the article induced topology on nLab meta. It was actually an accident. As Todd mentioned, I got sidetracked.

Todd, I would really appreciate it if you would move the article from nLab meta to the real nLab. I will add some more stuff by this weekend.

Once again, my apologies.
• CommentRowNumber14.
• CommentAuthorEric
• CommentTimeOct 28th 2010

???

• CommentRowNumber15.
• CommentAuthorTobyBartels
• CommentTimeOct 28th 2010
• (edited Oct 28th 2010)

There’s already an article induced topology on the main lab, but it discusses only subspace topologies. I moved Vishal’s text to weak topology, which was identified on induced topology as the name of the article on the more general concept. Then I moved induced topology to subspace topology, so that its name would make it more clear as to what it was about.

This leaves induced topology to redirect to subspace topology. But perhaps it should really redirect to weak topology? (I never use the term ‘induced topology’, preferring ‘subspace topology’ or ‘weak topology’ as appropriate.)

• CommentRowNumber16.
• CommentAuthorTodd_Trimble
• CommentTimeOct 28th 2010

What do the question marks mean in #14?

• CommentRowNumber17.
• CommentAuthorTodd_Trimble
• CommentTimeOct 28th 2010

Looks good, Toby. I think Vishal told me that his reference was The Joy of Cats, so maybe he can put that in as a reference (with a page number, if appropriate), when he has a chance.

• CommentRowNumber18.
• CommentAuthorUrs
• CommentTimeOct 28th 2010

I don’t think there’s much to discuss;

That was meant to be irony. I was getting worried that it might have been to the point of being offensive, but if it’s not even being understood, i can relax. ;.)

• CommentRowNumber19.
• CommentAuthorTodd_Trimble
• CommentTimeOct 28th 2010

It did look ironical. But what with the triple question marks and “Nm”s with which people communicate, it’s perhaps safer to act dumb sometimes. ;-)

• CommentRowNumber20.
• CommentAuthorTobyBartels
• CommentTimeNov 1st 2010

There really is one thing worth discussing: whether induced topology should redirect to subspace topology or to weak topology. If (as the former article suggests) that term is used primarily for the subspace topology, then leave it as it is (redirecting to that article). However, if (as the latter article suggests) that term is often used for any weak topology, then it probably should really redirect to the latter.

In the latter case, an alternative is to give induced topology its own article explaining how it’s used. But then weak topology is also used in special cases.

Speaking of which, I added a paragraph on the meaning in functional analysis.

• CommentRowNumber21.
• CommentAuthorTim_Porter
• CommentTimeNov 3rd 2010

4351 I note there are a lot of new entries recently!!! :-)

• CommentRowNumber22.
• CommentAuthorzskoda
• CommentTimeNov 22nd 2010
• (edited Nov 22nd 2010)

4470 entries and six non-full days before the birthday – close to 4500

• CommentRowNumber23.
• CommentAuthorUrs
• CommentTimeNov 22nd 2010

I won’t have much time for celebration activity, but it would be nice if we had some kind of post to the Café. Maybe somebody feels like compiling something.

• CommentRowNumber24.
• CommentAuthorzskoda
• CommentTimeNov 22nd 2010

I will not take any responsibility as there is lots of uncertainties about my urgent activities in next few days. But maybe I will be able to do something. I just submitted one paper of mine, but there are 4-5 activities still of importance till next Monday…

• CommentRowNumber25.
• CommentAuthorzskoda
• CommentTimeNov 25th 2010
Regarding that it is 4504 and that maybe we will not be around I will try to use the next box as the scratchbox for the part of future entry, if somebody wants to post it in original or by adding something to it. As a newcomer to cafe posting, I assume that links in the form [name](http:etc) work from top posts in cafe.
• CommentRowNumber26.
• CommentAuthorUrs
• CommentTimeNov 25th 2010
• (edited Nov 25th 2010)

As a newcomer to cafe posting, I assume that links in the form … work from top posts in cafe.

Should work, yes.

• CommentRowNumber27.
• CommentAuthorzskoda
• CommentTimeNov 25th 2010
• (edited Nov 26th 2010)

Over 4500 entries in the nLab and its 2nd birthday!

Guest post by Zoran Škoda (list additional names if apply)

The first entry of the n-Category Lab wiki appeared on November 28, 2008 02:18:19 marking the creation of the nLab; hence this Sunday morning it is 2 years old! Three days before the birthday its nominal count of pages reached 4500. This may be a proper moment to celebrate its wide usability already at its tender age and even more to invite people to use it more, and if possible to contribute. Like in our earlier update from May, we would like to point to some highlights in $n$Lab. But I somewhat run out of steam to dwell this time on the content and will rather outline some improvements in the content organization of the $n$Lab which may make it more attractive to you.

In my impression, in its first year, the $n$Lab was focused on our daily research needs and central areas of our interest: category theory, including higher, topoi, homotopy theory, topology, sheaves, stacks, simplicial objects, descent, cohomology (including differential), foundations and categorical aspects of physics. I have received signals from some users of $n$Lab that they do not contribute because they “do more concrete things”, say Lie algebras, representation theory, mathematical physics and so on and feel not to write about categories. But this is misunderstanding: more stuff in related areas is very welcome and we need contributors telling us the story in nearby areas of algebra, mathematical physics, differential geometry and so on (of course, not that far area that we can not understand, appreciate and connect to).

Regarding that we started in a bit self-centered areas of categorical mathematics it was difficult, in the first year, for a newcomer, to navigate through nLab and find out what interesting (s)he can find there. Hence, in the last several months large activity was centered not only in creating new content but also around new lists/tables of pointers of content in particular fields of interest. In this vein, Urs has been very enthusiastic in adding floating tables of contents. For example, each entry in topos theory, e.g. subobject classifier has a floating table of contents for Topos theory on its right-hand side. It is a pull-down menus which helps you navigate through entries in the subject of the particular table. Even the HomePage uses one floating table, to help the newcomer, and there are top level tables for mathematics and for physics. One can navigate top-down to some subsubjects from there.

Another organizational change in the last about a year is that most discussions which would earlier take place in query boxes in $n$Lab entries shifted to the nForum, which is well structured for many-purpose activities, thanks to the software and maintenance care of Andrew Stacey. Some of the discussions are about spams, bugs, writing, future policies and software, while some are about mathematical research, where Todd, Toby, Urs, Domenico, Jim, Tim, Mike, John, David and others explain extensively each others their insight. Some of the longer among such discussions happen in Atrium section, especially under Mathematics, Physics and Philosophy.

I have personally made effort to connect $n$Lab to the external sources of information and replaced previous Online Resources page by a network of several resource pages including:

• top page math resources
• page math blogs (previous Online Resources) with list of blogs and wikis
• page math institutions with a selected list of top world institutes and links to AMS-maintained and some other lists of math societies and departments
• page math archives with a list of main archives of online content in areas of our interest; with few exceptions (like MathSciNet), subscription sites are avoided and free archives preferred
• page math resources by individuals where there are some extremely rich pages of individuals in the prime areas of $n$Lab (there are hundreds of pages on individual mathematicians in $n$Lab, here we list just few particularly useful links)
• page books and reviews in mathematical physics with selected list of major research level books in mathematical physics

While in the first year the physics entries were dwarfed by the mathematical part of $n$Lab, now we do have a non-negligeable physics content. We recommend an outline of the nPOV in physics in the entry (mainly by Urs Schreiber)

Some picture of $n$Lab’s physics content can be accessed from the links at the top page physicscontents.

• CommentRowNumber28.
• CommentAuthorzskoda
• CommentTimeNov 25th 2010
• (edited Nov 25th 2010)

Hmm, above stub about organizational entries already hit the size limit for comment in nForum. In any case I am tired for today. Maybe somebody would like to add several paragraphs about some highlights in content or we may do that in next digest, say the Christmas Digest of nLab which may be quite soon.

• CommentRowNumber29.
• CommentAuthorzskoda
• CommentTimeNov 25th 2010

Some improvements to 27 are just entered.

• CommentRowNumber30.
• CommentAuthorUrs
• CommentTimeNov 25th 2010

Looks good to me. Thanks for writing this.

• CommentRowNumber31.
• CommentAuthorTobyBartels
• CommentTimeNov 26th 2010

Grammar correction the the first clause:

The $n$-Category Lab wiki was created with its first entry on November 28, 2008 02:18:19;

(There are other mistakes typical of you in the rest of what you’ve written, but I don’t think that they matter very much. However, the first sentence is more important.)

• CommentRowNumber32.
• CommentAuthorDavid_Corfield
• CommentTimeNov 26th 2010

Good job Zoran. So is there a preference as to when to post it? The birthday itself? And who’s going to post it?

• CommentRowNumber33.
• CommentAuthorzskoda
• CommentTimeNov 26th 2010

I think it may be cumbersome to post it on Sunday early morning. Regarding that we passed 4500 and are in the expectation of the weekend, I would ask a volunteer to post it now and inform others of the move. Unless of course, somebody wants to work more and add another few paragraphs, say on recent content highlights. If not, we could make a content announcment in something like the Christmas nLab Digest which may be posted one or two weeks before Christmas if people decide so (like the Christmas colloqiua in the universities do).

I rewrote the first sentence, I hope it is grammatically correct now. I was writing consistently $n$lab in the post, some prefer $n$Lab, it is up to you if you like to change it (or if you like me to change it).

• CommentRowNumber34.
• CommentAuthorzskoda
• CommentTimeNov 26th 2010
• (edited Nov 26th 2010)

OK I changed all to $n$Lab. Edit: including in the title where I avoided LaTeX $n$.

• CommentRowNumber35.
• CommentAuthorDavid_Corfield
• CommentTimeNov 26th 2010

OK. It’s up at the Cafe.

• CommentRowNumber36.
• CommentAuthorzskoda
• CommentTimeNov 26th 2010
Thanks. I hope it spreads some awareness.
• CommentRowNumber37.
• CommentAuthorUrs
• CommentTimeNov 26th 2010

Thanks!

• CommentRowNumber38.
• CommentAuthorTim_Porter
• CommentTimeNov 26th 2010

It looks good. Let us hope that we get some more contributions.

• CommentRowNumber39.
• CommentAuthorzskoda
• CommentTimeAug 22nd 2011
• (edited Aug 22nd 2011)

5500 pages by 300 authors - Last Update: August 22, 2011 22:51:48

Last Document: noncommutative Fourier transform Created by Zoran Škoda (161.53.130.104)

I wanted to create quantum group Fourier transform as it is related to something I am doing right now in research. But I have a sanitary problem which happened in my appartment over the weekend and will have to cut some hours from work tomorrow and go early home tonight. So I created first the page noncommutative Fourier transform on another topic, closer to other users of $n$Lab to make easier the disambiguation and will leave more ambitious (from the point of my own intentions in $n$Lab) “quantum group” case for later (probably not this week, I am likely out of any work later part of the week).

• CommentRowNumber40.
• CommentAuthorUrs
• CommentTimeAug 22nd 2011
• (edited Aug 22nd 2011)

5500 pages by 300 authors

It would be nice to make a new “digest” blog post. But I don’t feel that I have the time to look into this at the moment. If however anyone feels like writing something, I’d be happy to forward it to the blog. We could aim for 5555 entries.

• CommentRowNumber41.
• CommentAuthorzskoda
• CommentTimeSep 8th 2011

We are at 5612 pages, so 5555 is not that much of a good target any more :) Maybe 5678 or 6000 may be more realistic.

• CommentRowNumber42.
• CommentAuthorzskoda
• CommentTimeOct 5th 2011
• (edited Oct 5th 2011)

5697 $n$Lab pages at the moment. Edit: 5700 pages by 310 authors - Last Update: October 5, 2011 21:49:14.