From: "Prof. Peter Johnstone" <P.T.Johnstone@dpmms.cam.ac.uk>
To: "Ellis D. Cooper" <xtalv1@netropolis.net>, categories@mta.ca
Subject: Simple Situation
Date: Mon, 7 Dec 2009 15:37:33 +0000 (GMT) [thread overview]
Message-ID: <E1NHog6-0001yX-EE@mailserv.mta.ca> (raw)
In-Reply-To: <E1NGecr-0006DH-E3@mailserv.mta.ca>
If I've understood it right, this is exactly the concept of a
"multi-terminal object" (that is, a multi-limit for the empty
diagram). The name is due to me (in a paper called "A syntactic
approach to Diers's localizable categories" in SLNM 753 (1979)),
but the concept is due to Yves Diers: see his "Familles
universelles de morphismes", Ann. Soc. Sci. Bruxelles 93 (1979).
Peter Johnstone
On Fri, 4 Dec 2009, Ellis D. Cooper wrote:
> Dear categorists,
>
> Let C be a category with a distinguished sub-category E and a
> distinguished family S of morphisms
> such that for every object x of C there is a unique morphism f_x: x
> ---> e_x with e_x an object of E
> so that the following conditions are satisfied: (1) if x is in E then
> f_x = 1_x (the identity morphism
> of x), (2) if s: x ---> y is in S then e_y = e_x and f_x = f_y s.
>
> Hasn't this simple situation been named and incorporated in some
> publication on category
> theory? A reference would be most appreciated.
>
> Ellis D. Cooper
>
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prev parent reply other threads:[~2009-12-07 15:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-04 17:26 Ellis D. Cooper
2009-12-07 15:37 ` Prof. Peter Johnstone [this message]
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