From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/8392 Path: news.gmane.org!not-for-mail From: Michael Barr Newsgroups: gmane.science.mathematics.categories Subject: Re: Contact with Grothendieck Date: Tue, 18 Nov 2014 05:32:23 -0500 (EST) Message-ID: References: Reply-To: Michael Barr NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1416357130 8363 80.91.229.3 (19 Nov 2014 00:32:10 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 19 Nov 2014 00:32:10 +0000 (UTC) Cc: categories@mta.ca To: John Duskin Original-X-From: majordomo@mlist.mta.ca Wed Nov 19 01:32:04 2014 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtp3.mta.ca ([138.73.1.127]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XqtBk-0007HG-1C for gsmc-categories@m.gmane.org; Wed, 19 Nov 2014 01:32:04 +0100 Original-Received: from mlist.mta.ca ([138.73.1.63]:39702) by smtp3.mta.ca with esmtp (Exim 4.80) (envelope-from ) id 1XqtB7-0004rP-To; Tue, 18 Nov 2014 20:31:25 -0400 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1XqtB8-0000Cw-VE for categories-list@mlist.mta.ca; Tue, 18 Nov 2014 20:31:26 -0400 In-Reply-To: Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:8392 Archived-At: I met Grothendieck only once, in the summer of 1971. There was a NATO-spon= sored logic conference in, I think, England and some people decided to spon= sor a counter conference that would have no connection with anything milita= ry. It was held in a private boarding school in a town called Uldum, Denma= rk which is something like 50 km south of Aarhus. G. had given up mathemat= ics at that time and agreed to come presumably because it was anti-military= . I was spending half of that summer in Aarhus and I had a car, so on the d= ay G. was scheduled to speak, I got in my car and drove down. His talk was= interesting. As I recall, he stated the Giraud axioms for a topos and the= n said that to him, they looked an awful lot like set theory and logicians = should study them from that point of view. Maybe he said intuitionistic se= t theory; I don't recall. Well the Giraud axioms didn't--and don't--look m= uch like set theory to me. So at the end of his talk I asked him if he was= familiar with the Lawvere-Tierney axioms for a topos, which looked a lot m= ore like set theory than the Giraud axioms. He said that he didn't know wh= at they were and asked me to come to the board and explain them. Which I d= id (I added complete and cocomplete to recover the original definition that= G. had used). He agreed that looked a lot more like set theory. A few lo= gicians did study toposes, but whether they were motivated by G.'s lecture,= I can't tell you. After that we had an hour-long discussion of Survivre, = which didn't convince me. Bill can correct me if I am wrong, but I recall that at the Nice meeting a = year earlier, Bill had tried to tell him about elementary toposes, but G. w= asn't interested in anything mathematical. Michael [For admin and other information see: http://www.mta.ca/~cat-dist/ ]