From: Toby Bartels <toby+categories@math.ucr.edu>
To: categories@mta.ca
Subject: Re: Exactness without pullbacks
Date: Fri, 19 Jan 2007 08:33:20 -0800 [thread overview]
Message-ID: <E1H83FI-00026G-Dc@mailserv.mta.ca> (raw)
Michael Barr wrote:
>Toby Bartels wrote:
>>Has anybody considered (and are there any references with standard results)
>>categories that do *not* have *all* pullbacks
>>but nevertheless have some nice exactness properties?
>My recollection is that in the original definition only pullbacks of
>regular epis as well as kernel pairs were assumed to exist.
By "the original definition", you mean the definitions here?:
Michael Barr, Exact categories,
in Exact Categories and Categories of Sheaves,
Lecture Notes in Mathematics 236, Springer-Verlag, 1971.
I've never read this, since you-exact categories are now standard,
but I guess that one should always go back to the source!
--Toby
next reply other threads:[~2007-01-19 16:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-19 16:33 Toby Bartels [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-01-22 17:04 Eduardo Dubuc
2007-01-20 3:15 Michael Barr
2007-01-19 18:35 Eduardo Dubuc
2007-01-19 14:23 Michael Barr
2007-01-19 6:36 Toby Bartels
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