From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3408 Path: news.gmane.org!not-for-mail From: John Baez Newsgroups: gmane.science.mathematics.categories Subject: Martins-Porter paper Date: Mon, 28 Aug 2006 18:01:21 -0700 Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=3Diso-8859-1 Content-Transfer-Encoding: 8bit X-Trace: ger.gmane.org 1241019286 8604 80.91.229.2 (29 Apr 2009 15:34:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:34:46 +0000 (UTC) To: categories Original-X-From: rrosebru@mta.ca Wed Aug 30 18:35:23 2006 -0300 X-Keywords: Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Wed, 30 Aug 2006 18:35:23 -0300 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.61) (envelope-from ) id 1GIXYv-0001Nq-J4 for categories-list@mta.ca; Wed, 30 Aug 2006 18:25:29 -0300 Content-Disposition: inline User-Agent: Mutt/1.4.2.1i Original-Sender: cat-dist@mta.ca Precedence: bulk Original-Lines: 28 Xref: news.gmane.org gmane.science.mathematics.categories:3408 Archived-At: Interesting letter from Grothendieck! Ronnie Brown writes: >A recent arXiv paper by Jo=E3o Faria Martins and Tim Porter >math.QA/0608484 >Title: On Yetter's Invariant and an Extension of the Dijkgraaf-Witten >Invariant to Categorical Groups > > seems also relevant to the theme of the Baez-Shulman notes. Yes; we didn't get into TQFTs at all in our notes, but Martins and Porter use the classifying space of a discrete 2-group (=3D categorical group =3D crossed module =3D gr-category) in their construction, and that's quite relevant. I wrote a little introduction to the Martins-Porter paper and its antecedents at the n-category cafe: http://golem.ph.utexas.edu/category/2006/08/categorifying_the_dijkgraafwit.= html Best, jb