From: "Fred E.J. Linton" <fejlinton@usa.net>
To: Mark Spezzano <mark.spezzano@chariot.net.au>, <categories@mta.ca>
Subject: Re: Are there exactly 11 categories with 3 arrows?
Date: Fri, 26 Mar 2010 22:03:30 -0400 [thread overview]
Message-ID: <E1Nvbri-0005wN-AY@mailserv.mta.ca> (raw)
On Fri, 26 Mar 2010, at 08:09:06 PM EDT, Mark Spezzano
<mark.spezzano@chariot.net.au> asked:
> Are there exactly 11 categories with 3 arrows?
Some gentle hints, without giving away the answers:
> ... I need to cover three possibilities:
>
> a) One object with three arrows. How many are there of these?
That's the heart of the problem: how many monoid structures
can be imposed on the identity and the two non-identity arrows?
> b) Two objects with three arrows. How many are there of these?
Where can the single non-identity arrow be?
> c) Three objects with three arrows. ... the answer to this ... is 1 ...
Agreed. HTH. Cheers, -- Fred
[For admin and other information see: http://www.mta.ca/~cat-dist/ ]
next reply other threads:[~2010-03-27 2:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-27 2:03 Fred E.J. Linton [this message]
2010-03-27 23:40 ` Vaughan Pratt
-- strict thread matches above, loose matches on Subject: below --
2010-03-26 14:07 Mark Spezzano
2010-03-27 0:45 ` David Roberts
2010-03-27 1:01 ` Aleks Kissinger
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