From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/5526 Path: news.gmane.org!not-for-mail From: "Hans-Peter Stricker" Newsgroups: gmane.science.mathematics.categories Subject: Examples for the Yoneda lemma Date: Fri, 15 Jan 2010 01:24:52 +0100 Message-ID: Reply-To: "Hans-Peter Stricker" NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain;format=flowed;charset="iso-8859-1";reply-type=original Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1263524983 28368 80.91.229.12 (15 Jan 2010 03:09:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 15 Jan 2010 03:09:43 +0000 (UTC) To: Original-X-From: categories@mta.ca Fri Jan 15 04:09:36 2010 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 4.50) id 1NVcZ5-00013e-Ug for gsmc-categories@m.gmane.org; Fri, 15 Jan 2010 04:09:36 +0100 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1NVc0f-0007c0-QE for categories-list@mta.ca; Thu, 14 Jan 2010 22:34:01 -0400 Original-Sender: categories@mta.ca Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:5526 Archived-At: Hello, I am looking for (simple) instructive examples for the Yoneda lemma, showing how to get the "inner" structure of an object from its morphisms. I've been told how to get a graph G from its morphisms (from the one-vertex-graph V to G and the one-edge-graph E to G and the morphisms from V to E) and appreciated this example a lot. Are there others equally simple and enlightening? What I wonder is which morphisms are definitely needed. In the graph example it's the morphisms from V -> G, E -> G and V -> E? Can this be abstracted and generalized? Many thanks in advance Hans-Stricker [For admin and other information see: http://www.mta.ca/~cat-dist/ ]