From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/6136 Path: news.gmane.org!not-for-mail From: David Leduc Newsgroups: gmane.science.mathematics.categories Subject: Evil in bicategories Date: Sat, 11 Sep 2010 02:05:37 +0000 Message-ID: Reply-To: David Leduc NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: dough.gmane.org 1284214685 22969 80.91.229.12 (11 Sep 2010 14:18:05 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Sat, 11 Sep 2010 14:18:05 +0000 (UTC) To: categories Original-X-From: majordomo@mlist.mta.ca Sat Sep 11 16:18:04 2010 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtpy.mta.ca ([138.73.1.139]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1OuQu3-0007EW-Gb for gsmc-categories@m.gmane.org; Sat, 11 Sep 2010 16:18:03 +0200 Original-Received: from mlist.mta.ca ([138.73.1.63]:57921) by smtpy.mta.ca with esmtp (Exim 4.71) (envelope-from ) id 1OuQsX-0006SZ-K9; Sat, 11 Sep 2010 11:16:29 -0300 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1OuQsT-0003hL-P6 for categories-list@mlist.mta.ca; Sat, 11 Sep 2010 11:16:25 -0300 Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:6136 Archived-At: In a bicategory, composition of 1-cells is associative up to isomorphism. Because it would be evil to insist that h o (g o f) is equal to (h o g) o f. However the source and target objects of those compositions must be equal. Isn't it evil? Why not weaken this requirement by saying that the sources (respectively, targets) of h o (g o f) and (h o g) o f must only be isomorphic? [For admin and other information see: http://www.mta.ca/~cat-dist/ ]