From: jim stasheff <[email-masked]>
Date: Wed, 15 Mar 2006 20:53:54 -0500

To [email-masked]
Subject: categories: Re: cracks and pots
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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
>> [email-masked]
>> http://www.math.mcgill.ca/bunge/
>> ************************************************
>>
>>
>>
>>