From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/1086 Path: news.gmane.org!not-for-mail From: Francois Lamarche Newsgroups: gmane.science.mathematics.categories Subject: They often come in pairs Date: Fri, 19 Mar 1999 14:51:20 +0100 Organization: LORIA Message-ID: <36F25658.4F862077@loria.fr> References: <199903181931.TAA02244@wax.dcs.qmw.ac.uk> NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241017556 29438 80.91.229.2 (29 Apr 2009 15:05:56 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:05:56 +0000 (UTC) To: categories@mta.ca Original-X-From: cat-dist Fri Mar 19 12:24:19 1999 Original-Received: (from Majordom@localhost) by mailserv.mta.ca (8.9.3/8.9.3) id JAA22497 for categories-list; Fri, 19 Mar 1999 09:55:58 -0400 (AST) X-Authentication-Warning: mailserv.mta.ca: Majordom set sender to cat-dist@mta.ca using -f X-Mailer: Mozilla 4.5 [en] (X11; I; SunOS 5.5 sun4m) X-Accept-Language: fr, en Original-Sender: cat-dist@mta.ca Precedence: bulk Original-Lines: 27 Xref: news.gmane.org gmane.science.mathematics.categories:1086 Archived-At: Perhaps some precisions should be added to Paul's msg. > Another model, whose types are named by countable groupoids (or by the > corresponding presheaf toposes of G-sets) is to be found in my paper > "Quantitative Domains, Groupoids and Linear Logic" in the proceedings > of the 1989 Manchester CTCS. When I was writing this paper I tried to > get Francois Lamarche to read it, but he said he didn't know anything > about / hated permutation representations. Nobody else, so far as I can > gather, has ever read it, and now I can no longer follow the most > difficult calculations. However, it is a very pretty model nevertheless. Because of my thesis' work (on not-unrelated subjects to those mentioned by Paul) I had already dealt with permutations in power types when Paul started pushing his groupoid models. They indeed give rise to "the most horrendous mess". This was a long time ago, my memory is vague, but I probably told him, or hinted, that in my opinion they were most likely a blind alley. I still think that if I started working again in this field, the problem I would zero in would be to get rid of the permutation groups, by "unraveling" them by the means of actions (the groupoid associated with the action of a group on a set can be made much simpler than the group itself). The point of semantics is to give you insights about the logic, so simplicity is... a big plus. And since I refereed his CTCS paper, I *did* read it. Francois