From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/6704 Path: news.gmane.org!not-for-mail From: "Fred E.J. Linton" Newsgroups: gmane.science.mathematics.categories Subject: Re: Codensity and the ultrafilter monad Date: Thu, 09 Jun 2011 21:04:15 -0400 Message-ID: Reply-To: "Fred E.J. Linton" 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 1307695734 25364 80.91.229.12 (10 Jun 2011 08:48:54 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Fri, 10 Jun 2011 08:48:54 +0000 (UTC) To: Tom Leinster , Original-X-From: majordomo@mlist.mta.ca Fri Jun 10 10:48:49 2011 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtpx.mta.ca ([138.73.1.30]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1QUxOZ-0004xx-Dk for gsmc-categories@m.gmane.org; Fri, 10 Jun 2011 10:48:47 +0200 Original-Received: from mlist.mta.ca ([138.73.1.63]:32815) by smtpx.mta.ca with esmtp (Exim 4.71) (envelope-from ) id 1QUxML-0000A0-6Z; Fri, 10 Jun 2011 05:46:29 -0300 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1QUxMK-0000LL-Ht for categories-list@mlist.mta.ca; Fri, 10 Jun 2011 05:46:28 -0300 Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:6704 Archived-At: Tom Leinster wrote, in part: > The codensity monad of the inclusion FinSet --> Set is the ultrafilter = > monad. This seems a rather basic fact, but I've been unable to find it= in = > the literature. I'd be grateful if someone could tell me a reference. I can't be certain, but I can easily imagine Oswald Wyler or = Ernie Manes having noticed that fact in the dim, dark, distant past. Perhaps Ernie will chime in :-) . HTH. Cheers, -- Fred [For admin and other information see: http://www.mta.ca/~cat-dist/ ]