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May 10, 2016

The Works of Charles Ehresmann

Posted by John Baez

Charles Ehresmann’s complete works are now available for free here:

There are 630 pages on algebraic topology and differential geometry, 800 pages on local structures and ordered categories, and their applications to topology, 900 pages on structured categories and quotients and internal categories and fibrations, and 850 pages on sketches and completions and sketches and monoidal closed structures.

That’s 3180 pages!

On top of this, more issues of the journal he founded, Cahiers de Topologie et Géométrie Différentielle Catégoriques, will become freely available online.

Andrée Ehresmann announced this magnificent gift to the world on the category theory mailing list, writing:

We are pleased to announce that the issues of the Cahiers de Topologie et Géométrie Différentielle Catégoriques, from Volume L (2009) to LV (2014) included, are now freely downloadable from the internet site of the Cahiers:

http://ehres.pagesperso-orange.fr/Cahiers/Ctgdc.htm

through the hyperlink to Recent Volumes.

In the future the issues of the Cahiers will become freely available on the site of the Cahiers two years after their paper publication. We recall that papers published up to Volume XLIX are accessible on the NUMDAM site.

Moreover, the 7 volumes of Charles Ehresmann: Oeuvres complètes et commentées (edited by A. Ehresmann from 1980-83 as Supplements to the Cahiers) are now also freely downloadable from the site

http://ehres.pagesperso-orange.fr/C.E.WORKSfichiers/C.EWorks.htm

These 2 sites are included in the site of Andrée Ehresmann

http://ehres.pagesperso-orange.fr/

and they can also be accessed through hyperlinks on its first page.

Sincerely,

Andree Ehresmann, Marino Gran and Rene Guitart,

Chief-Editors of the Cahiers

Posted at May 10, 2016 3:51 PM UTC

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Re: The Works of Charles Ehresmann

In the future the issues of the Cahiers will become freely available on the site of the Cahiers two years after their paper publication.

That’s great. Of course, it would be greater still if they were freely available immediately, but I can imagine the kind of reasons why the editors aren’t doing this, and I don’t have a solution.

One reason why I’d really like Cahiers to be freely available immediately is that Theory and Applications of Categories needs a competitor.

I’m very pro-TAC, I’m an editor, and I want people to submit their best category theory work to it. However, there’s a shortage of attractive journals that publish category theory papers, so the quality within TAC is quite mixed. Cahiers unfortunately makes itself less attractive by not making its papers freely available immediately (unlike TAC, which does). Of course, authors can arXiv, but it’s not the same.

Cahiers has a long and proud history of publishing important papers in category theory, and I’ve been wishing for a while that it could offer the same kind of free-to-everyone service that TAC does.

Posted by: Tom Leinster on May 10, 2016 8:40 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Of course, authors can arXiv, but it’s not the same.

Why is it not the same? The only differences usually between an arxiv’d version and a published version are typesetting and/or typos (and sometimes published versions have more typos then the arxiv versions).

Posted by: Eugene Lerman on May 11, 2016 3:19 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

The arXiv’s great and I put almost all my papers on it. All the same, it makes a real difference that the whole TAC content is available for free, for everyone, right there on the web page. If you’re looking for a paper in TAC, you just go to the web site and there it is. You don’t have to go hunting round to see if it’s on the arXiv or the author’s web page or what, and you don’t have to worry about post-refereeing or pre-refereeing versions. I think that’s one of the attractions of TAC.

(Though I agree that in general, journals sometimes make things worse at the level of typos and formatting.)

Posted by: Tom Leinster on May 11, 2016 1:43 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

The mere obscurity, despite its quality, of a journal can rule out its use by authors and readers. Something published by a retired French professor may be seen as a little too niche. For instance, the Cahiers didn’t get a ranking by the Australian Mathematical Society, whereas TAC did (I don’t like the rankings, and wish they’d vanish, but people use them as a guide still).

Posted by: David Roberts on May 11, 2016 7:24 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

It may be relatively obscure now, but it needn’t be in the future. I’d hope for Cahiers to build on its base of quality and its reputation among category theorists, to become a better-known, more widely accessible, more widely accessed, higher-reputation journal.

Posted by: Tom Leinster on May 11, 2016 1:45 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Cahiers is not considered obscure by category theorists: it’s a good journal. Unfortunately, category theory is considered obscure by most mathematicians, and many Anglophones consider French obscure.

There’s no reason why academics should value a journal published by a “retired French professor” any less than one published by a price-gouging conglomerate like the Holtzbrinck Publishing Group / Nature Publishing Group (the company that owns Springer). What matters is the quality of the papers, the services provided by the journal and its editors, and the value for money: in particular, the amount of content that’s made available for free. On that score Cahiers beats something like Applied Categorical Structures hands down, as far as I’m concerned.

If some organization ranking journals didn’t bother to rank Cahiers, or ranked it less highly than it should be, someone should tell them to shape up. In the case of the Australian Mathematical Society, it would make sense for some Australian category theorists to do this.

Somebody needs to rank these ranking systems. If we just kneel down and accept them, academia is doomed.

Posted by: John Baez on May 11, 2016 5:44 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Certainly among category theorists it’s not obscure! I couldn’t convince my library to subscribe, though there are clearly confounding factors there. I had plans to send something to Cahiers soon, but the wow-factor of the result grew somewhat, till I thought it perhaps deserved a wider audience. I certainly will keep an up-to-date version on the arXiv, so why do I hesitate? Shouldn’t I help improve the (perceived) quality of what I think is a good journal that deserves my support, for what that’s worth? I have a co-author to think of as well, though he’s the one with the permanent job. But in all honesty, I would love to just send my paper wherever I like, and let the arXiv deal with the distribution. But if, say, Geometry and Topology, or Proceedings of the LMS publishes my paper, people view it differently to if Cahiers publishes it, rightly or wrongly.

I too wish for Cahiers to become more widely accessible, and emerge as a thoroughly modern journal with a long history, much as I’d like TAC to emerge from the 1990s and become an open access journal befitting the 21st century. I’ve had little luck talking with TAC editors so far about this, so Cahiers I imagined would be even slower to respond…

Posted by: David Roberts on May 12, 2016 1:25 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

David wrote:

[…] much as I’d like TAC to emerge from the 1990s and become an open access journal befitting the 21st century.

What’s the problem with TAC? The copyright rules?

The way for us to improve TAC is to become editors (like Tom is) and do some work to improve it.

I was an editor for a while, but I found I have a strong distaste for persuading people to be referees, forcing them to write referee reports, etc. It’s unfortunate.

Posted by: John Baez on May 12, 2016 2:18 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Licensing is probably my biggest bugbear. What the heck is ‘private use’? And if and when an author passes away? (eg Brian Day) Who gets to say what happens with their papers if people would like to do something with them, like make a ‘collected works’ volume?

Secondly, I’m sure something like an RSS feed wouldn’t be too hard to set up. Perhaps the current ‘subscription’ method is good for getting a concrete measure on the readership numbers, but the more ways to get news out, the better.

DOIs cost money, so Bob was not keen on those at all. But they do not cost much, if someone had spare grant money to donate (cf Discrete Analysis, where article processing costs 10 dollars a paper, and that’s for more than a DOI!)

Seeing as I’m currently what people in the US call an ‘adjunct’, at best, I’m hardly in a position to become an editor of what is arguably the flagship category theory journal.

Posted by: David Roberts on May 12, 2016 9:49 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Here is TAC’s copyright agreement. I don’t see anything about “private use”.

Posted by: Mike Shulman on May 12, 2016 6:43 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Look at the bottom of the front page of any TAC article. You will see

(c) [Author(s)], [year]. Permission to copy for private use granted.

I’m thinking about downstream users here.

Posted by: David Roberts on May 13, 2016 12:31 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

That seems like an okay license to me. The author keeps the copyright, while the journal gets the right to do certain things it needs to do: mainly, publish the paper. This seems better than the usual system where the journal gets the copyright and the author gets certain limited rights.

Posted by: John Baez on May 12, 2016 6:56 PM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Sure, it’s far better than the usual take-the-copyright-and-run approach of (most) commercial publishers. But it’s not as good as newer open access journals that benefit from the intensive legal drafting and consultation the Creative Commons licenses went through, all of which post-date the founding of TAC.

As I mentioned in my comment to Mike, readers and other downstream users get flaky promises they can use the article ‘privately’, whatever that means. Ask your university lawyers if they can make a judgement on what can and can’t be done with such a promise :-)

Posted by: David Roberts on May 13, 2016 12:34 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

On a separate note, some of the scanning of the pages in the OEuvres seems to have gone terribly wrong! There’s some pages where the text from the reverse side shows through, obscuring everything :-(

Posted by: David Roberts on May 12, 2016 1:27 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

I’m sure if you email Andrée with details she’d be very interested in getting the problem fixed. You have her email address from her message on the category theory mailing list. If for some reason you’re reluctant to contact her, let me know and I will. I’ve met her a few times, and she’s been very friendly.

On May 23rd 2014 I wrote:

This is the category theorist Andrée Ehresmann in an anechoic chamber, computer in hand. Yesterday we went into this room at IRCAM, a famous experimental music laboratory in Paris.

An anechoic chamber is a room with walls designed to absorb all incident sounds — if you snap your fingers, it sounds strangely dead, and one of my hosts said you can lose your sense of orientation. At IRCAM they sometimes suspend a piano inside the anechoic chamber to study its sounds without any echoes getting in the way.

IRCAM is the Institut de Recherche et Coordination Acoustique/Musique. From the outside it looks unimpressive, because most of the rooms are underground. Inside they’ve got a huge performance space where all the walls are speakers… using computers they can make sounds move around the room. And I got a great demonstration of OMax, a program that can listen to musicians, learn the patterns, and start to improvise along with them in real time.

Andrée Ehresmann is a mathematician who began as analyst but then worked on category theory with her husband Charles, developing concepts such as double categories, internal categories and the like, often for the study of differential geometry. At IRCAM she is working on music theory with Alexandre Popoff and Moreno Andreatta.

They’re studying K-nets, which are diagrams where the vertices are notes or chords, and the edges are musical operations like transposition (raising or lowering a note or chord) and inversion (flipping a note or chord upside down). K-nets were invented by a music theorist, but they’re easiest to define using some category theory. You start with a group G of musical operations (like the 24-element group of transpositions and inversions), think of it acting on a set S (like a set of notes or chords), and then look at a functor from a diagram D into G. Then the vertices of the diagram get labelled with notes or chords in S, while the edges get labelled with musical operations in G.

I had a great time, and hope to spend more time there someday when I return to Paris! Alas, I’m leaving the day after tomorrow.

Posted by: John Baez on May 12, 2016 2:13 AM | Permalink | Reply to this

Re: The Works of Charles Ehresmann

Thanks, I will compile a list of pages and let her know, but I wouldn’t be surprised if others have already noticed.

Posted by: David Roberts on May 12, 2016 9:53 AM | Permalink | Reply to this

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