From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/5852 Path: news.gmane.org!not-for-mail From: =?iso-8859-1?Q?Joyal=2C_Andr=E9?= Newsgroups: gmane.science.mathematics.categories Subject: Equality again Date: Mon, 24 May 2010 19:06:23 -0400 Message-ID: References: Reply-To: =?iso-8859-1?Q?Joyal=2C_Andr=E9?= NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Trace: dough.gmane.org 1274810123 7782 80.91.229.12 (25 May 2010 17:55:23 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Tue, 25 May 2010 17:55:23 +0000 (UTC) To: "Colin McLarty" , Original-X-From: categories@mta.ca Tue May 25 19:55:22 2010 connect(): No such file or directory Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from mailserv.mta.ca ([138.73.1.1]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1OGyLa-0002ig-0l for gsmc-categories@m.gmane.org; Tue, 25 May 2010 19:55:22 +0200 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1OGy6C-0003wd-Vf for categories-list@mta.ca; Tue, 25 May 2010 14:39:29 -0300 Thread-Topic: Equality again Thread-Index: Acr7QzcM+8KWDeApQhaqyzQ6b6EblgATsIpP Original-Sender: categories@mta.ca Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:5852 Archived-At: Dear Colin, You wrote: >It is an interesting impulse in higher category theory to avoid >identity in favor of isomorphism on the level of objects, and to avoid >isomorphism in favor of equivalence on the level of categories. But >so far as I know no one has yet articulated a way to avoid ever using >identity of objects and identity of categories. I love the equality symbol more than an isomorphism symbol, and an isomorphism symbol more than an equivalence symbol. I always try to use the equality symbol whenever possible. I often use the equality symbol for a canonical isomorphism. Is there a special symbol for canonical isomorphism? (as oppose to a plain isomorphism). I would love to write something like A times (B times C) =3D' (A times B) times C Andr=E9 -------- Message d'origine-------- De: categories@mta.ca de la part de Colin McLarty Date: dim. 23/05/2010 11:39 =C0: categories@mta.ca Objet : categories: Re: terminology =20 I have very much appreciated Andr=E9's subtlety on this issue in = conversation ... [For admin and other information see: http://www.mta.ca/~cat-dist/ ]