From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/7898 Path: news.gmane.org!not-for-mail From: Anders Kock Newsgroups: gmane.science.mathematics.categories Subject: Preprint available Date: Tue, 22 Oct 2013 08:03:53 +0000 Message-ID: Reply-To: Anders Kock NNTP-Posting-Host: plane.gmane.org Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1382538433 32174 80.91.229.3 (23 Oct 2013 14:27:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 23 Oct 2013 14:27:13 +0000 (UTC) To: "categories@mta.ca" Original-X-From: majordomo@mlist.mta.ca Wed Oct 23 16:27:16 2013 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtp3.mta.ca ([138.73.1.186]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VYzOu-0001SH-0o for gsmc-categories@m.gmane.org; Wed, 23 Oct 2013 16:27:08 +0200 Original-Received: from mlist.mta.ca ([138.73.1.63]:55684) by smtp3.mta.ca with esmtp (Exim 4.80) (envelope-from ) id 1VYzNv-0000ze-M7; Wed, 23 Oct 2013 11:26:07 -0300 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1VYzNu-0007cP-It for categories-list@mlist.mta.ca; Wed, 23 Oct 2013 11:26:06 -0300 Content-Language: da-DK Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:7898 Archived-At: My preprint "Projective lines as groupoids with projection structure" is no= w available at arXiv. A projection structure on a groupoid consists in giving, for each pair (A,B) of distinct objects in it, a bijection between the set hom(A,B), and the set of objects distinct from A and B. Groupoids with such structure occur naturally in projective geometry over a field. - The present note investigates when, conversely, an abstractly given groupoid with projection structure comes about from a field, constructed out of the groupoid. http://arxiv.org/abs/1310.5357 Anders [For admin and other information see: http://www.mta.ca/~cat-dist/ ]