From: Robert Pare <pare@mathstat.dal.ca>
To: categories@mta.ca
Subject: Undirected graphs
Date: Wed, 8 Mar 2006 11:07:20 -0400 (AST) [thread overview]
Message-ID: <20060308150720.9D5D07375B@chase.mathstat.dal.ca> (raw)
[note from moderator: resent due to faulty From: ]
I've been following the recent posts on undirected graphs
with interest. But I have a question. I think it's being said
that undirected graphs are the same as directed graphs with
involution. (Presheaves on the full subcategory of SET determined
by 1 and 2, or just 2.) Which is nice but what about loops?
The involution might fix a loop or not. So wouldn't we be
getting undirected graphs with two kinds of loops, whole loops
and semiloops? What am I missing?
Bob
next reply other threads:[~2006-03-08 15:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-08 15:07 Robert Pare [this message]
2006-03-09 6:56 ` Sebastiano Vigna
2006-03-10 17:17 ` Vaughan Pratt
2006-03-12 4:10 ` Vaughan Pratt
2006-03-13 0:51 ` F W Lawvere
2006-03-09 14:05 ` F W Lawvere
2006-03-10 8:07 ` Marco Grandis
-- strict thread matches above, loose matches on Subject: below --
2006-03-09 17:38 Chris Wensley
2006-03-02 18:16 Dr. Cyrus F Nourani
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