From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/3113 Path: news.gmane.org!not-for-mail From: jim stasheff Newsgroups: gmane.science.mathematics.categories Subject: (unknown) Date: Wed, 15 Mar 2006 20:53:54 -0500 Message-ID: <4418C532.20706@math.upenn.edu> NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 X-Trace: ger.gmane.org 1241019101 7300 80.91.229.2 (29 Apr 2009 15:31:41 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 15:31:41 +0000 (UTC) Original-X-From: rrosebru@mta.ca Thu Mar 16 05:29:10 2006 -0400 Return-path: Envelope-to: categories-list@mta.ca Delivery-date: Thu, 16 Mar 2006 05:29:10 -0400 Original-Received: from Majordom by mailserv.mta.ca with local (Exim 4.52) id 1FJoia-0005na-9f for categories-list@mta.ca; Thu, 16 Mar 2006 05:24:28 -0400 User-Agent: Thunderbird 1.5 (Windows/20051201) Original-Lines: 143 Xref: news.gmane.org gmane.science.mathematics.categories:3113 Archived-At: To categories@mta.ca Subject: categories: Re: cracks and pots References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: cat-dist@mta.ca Precedence: bulk Status: RO X-Status: X-Keywords: X-UID: 59 Mostly well said, David I would only modify/deform ;-) what you say by doubting therte are that many physicists who are anti-cat theory (not pro-) but watch out once some leader of the school adopts it the school will follow - much faster than if they were mathematicians jim David Yetter wrote: > 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/ >> ************************************************ >> >> >> >>