From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3093 Path: news.gmane.org!not-for-mail From: David Yetter Newsgroups: gmane.science.mathematics.categories Subject: Re: cracks and pots Date: Tue, 14 Mar 2006 01:08:49 -0500 Message-ID: References: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1241019090 7211 80.91.229.2 (29 Apr 2009 15:31:30 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:31:30 +0000 (UTC) To: categories@mta.ca Original-X-From: rrosebru@mta.ca Tue Mar 14 18:44:58 2006 -0400 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Tue, 14 Mar 2006 18:44:58 -0400 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1FJIDE-0002Lc-9T for categories-list@mta.ca; Tue, 14 Mar 2006 18:41:56 -0400 In-Reply-To: Original-Sender: cat-dist@mta.ca Precedence: bulk X-Keywords: X-UID: 39 Original-Lines: 117 Xref: news.gmane.org gmane.science.mathematics.categories:3093 Archived-At: Dear Marta, My reaction to the blog posts you cite is that this is a sting theorist holding his breath and refusing to learn category theory. My guess is that Motl wouldn't want to learn the heavily categorical formulations of mirror symmetry that Yan Soibelman uses, even though they are motivated by string theory. Basically categorical ideas aren't part of the standard bag of tricks physicists use (even though they often give much more elegant, concise, and insightful formulations of some of those tricks), and the proverb about 'old dogs' and 'new tricks' applies to physicists as well. His attack on Baez is fairly standard stuff: in the mode of "string theory is the theory of nature, so we don't want to think about alternatives like loop quantum gravity." It is a polemical defense of a scientific theory that hasn't produced a testable prediction in the 40 plus years since its inception, and worse than that, unless one adds bells and whistles to fix it (in the manner of 'gaseous Vulcan' or Ptolemaic epicycles), predicts the existence of a massless scalar field *not observed in nature*. It really has nothing at all to say about category theory, which is after all a mathematical theory which stands irrespective of its extra-mathematical applications. Categorical ideas are absolutely central to several competitors to string theory: the Barrett-Crane model of quantum gravity (and to a lesser extent 'loop quantum gravity' with which the BC model is often conflated) and Connes' recovery of the Standard Model from non-commutative geometry (a part of mathematics which has obliged reluctant mathematicians to think about categorical ideas deeper than they originally were comfortable with). There is nothing cracked or crackpot about either. It is simply a fact we have to live with that our subject has found legitimate uses in physics, but uses which are unpopular with the dominant school of physics in the North America. If (I suspect when) the string theory emperor turns out to have no clothes, category theory will suddenly become de rigeur in physics. (As it should, since categorical expressions of physical ideas are the logical conclusion of 20th century physics drive to express everything in coordinate-free terms.) Best Thoughts, David Yetter On 12 Mar 2006, at 17:29, Marta Bunge wrote: > Hi, > > I just came across the following pages > > http://motls.blogspot.com/2004/11/category-theory-and-physics.html > http://motls.blogspot.com/2004/11/this-week-208-analysis.html > > written by Lubos Motl, a physicist (string theorist). Some of you may > find > these articles interesting and probably revealing. > > Are we category theorists as a whole going to quietly accept getting > discredited by a minority of us presumably applying category theory to > string theory? It is surely not too late to react and point out that > this is > not what (all of) category theory is about. Please give a thought > about what > we, as a community, can urgently do to repair this damaging impression. > Unless we are prepared to wait until things change by themselves > within our > lifetime. > > > Hopefully disturbing your weekend, > Cordially, > Marta > > > > ************************************************ > Marta Bunge > Professor Emerita > Dept of Mathematics and Statistics > McGill University > 805 Sherbrooke St. West > Montreal, QC, Canada H3A 2K6 > Office: (514) 398-3810 > Home: (514) 935-3618 > marta.bunge@mcgill.ca > http://www.math.mcgill.ca/bunge/ > ************************************************ > >