From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3452 Path: news.gmane.org!not-for-mail From: Tom Leinster Newsgroups: gmane.science.mathematics.categories Subject: Paper: The Euler characteristic of a category Date: Tue, 10 Oct 2006 10:36:18 +0100 Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241019312 8814 80.91.229.2 (29 Apr 2009 15:35:12 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:35:12 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Tue Oct 10 22:08:33 2006 -0300 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 10 Oct 2006 22:08:33 -0300 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1GXSPr-0005gj-Uh for categories-list@mta.ca; Tue, 10 Oct 2006 21:57:48 -0300 Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 13 Original-Lines: 22 Xref: news.gmane.org gmane.science.mathematics.categories:3452 Archived-At: The following paper is available. It is the full version of the talk I gave at CT06. "The Euler characteristic of a category" The Euler characteristic of a finite category is defined and shown to be compatible with Euler characteristics of other types of object, including orbifolds. A formula is proved for the cardinality of a colimit of sets, generalizing the classical inclusion-exclusion formula. Both rest on a generalization of Mobius-Rota inversion from posets to categories. http://arxiv.org/abs/math.CT/0610260 Best wishes, Tom -- Tom Leinster