From: Tom Leinster <tl@maths.gla.ac.uk>
To: jds@math.upenn.edu
Subject: Re: query
Date: Fri, 26 Jun 2009 16:51:56 +0100 (BST) [thread overview]
Message-ID: <E1MKSGH-00028T-4o@mailserv.mta.ca> (raw)
Dear Jim,
On Wed, 24 Jun 2009, jim stasheff wrote:
> Mac Lane coherence can be deduced from the simple connectivity of the
> associahedron
Surely that's not true, assuming that by "Mac Lane coherence" you mean Mac
Lane's coherence theorem for monoidal categories. The associahedra (and
in particular the pentagon) say nothing about the unit coherence
isomorphisms,
X \otimes I ----> X <---- I \otimes X.
To make it true, surely you need to weaken Mac Lane's theorem to a
statement about "semigroupal" categories, i.e. monoidal categories without
unit...?
Best wishes,
Tom
[For admin and other information see: http://www.mta.ca/~cat-dist/ ]
next reply other threads:[~2009-06-26 15:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-26 15:51 Tom Leinster [this message]
-- strict thread matches above, loose matches on Subject: below --
2009-06-26 10:47 query Noson S. Yanofsky
2009-06-24 16:18 query jim stasheff
2008-07-17 8:35 Query Johannes Huebschmann
2003-10-02 12:55 query jim stasheff
2003-05-05 17:46 Query Oswald Wyler
[not found] <199811190226.NAA02248@macadam.mpce.mq.edu.au>
1998-11-20 23:06 ` query Michael Batanin
1998-11-19 9:31 query Marco Grandis
1998-11-19 1:15 query Ross Street
1998-11-18 4:12 query john baez
1998-11-16 22:08 query James Stasheff
1997-10-07 11:30 query categories
1997-10-02 19:52 query categories
1997-10-01 19:50 query categories
1997-07-01 18:14 Query categories
1997-07-01 2:41 Query categories
1997-07-01 2:39 Query categories
1997-06-29 14:39 Query categories
1997-02-10 15:52 query categories
1997-02-10 1:03 query categories
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