From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3448 Path: news.gmane.org!not-for-mail From: "Prof. Peter Johnstone" Newsgroups: gmane.science.mathematics.categories Subject: Re: Reflexive coequalizers Date: Mon, 9 Oct 2006 14:37:24 +0100 (BST) Message-ID: References: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Trace: ger.gmane.org 1241019310 8797 80.91.229.2 (29 Apr 2009 15:35:10 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:35:10 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Mon Oct 9 21:26:34 2006 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Mon, 09 Oct 2006 21:26:34 -0300 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1GX5OG-0005DQ-2D for categories-list@mta.ca; Mon, 09 Oct 2006 21:22:36 -0300 In-Reply-To: Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 9 Original-Lines: 22 Xref: news.gmane.org gmane.science.mathematics.categories:3448 Archived-At: On Mon, 9 Oct 2006, Richard Garner wrote: > > Dear categorists, > > I have a proof that the indiscrete category functor > Set -> Cat preserves reflexive coequalizers which, > although straightfoward, uses the explicit > description of colimits in Cat. Is this necessary, > or can I deduce the result from general > principles? > It certainly follows from the fact that reflexive coequalizers commute with finite products in Set (or in any cartesian closed category). This is a result that some people attribute to me, since the first place it was explicitly written down seems to have been my PhD thesis, though I'm sure it was known well before that. Peter Johnstone