From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/513 Path: news.gmane.org!not-for-mail From: categories Newsgroups: gmane.science.mathematics.categories Subject: Pratt slices Date: Tue, 4 Nov 1997 13:34:16 -0400 (AST) Message-ID: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Trace: ger.gmane.org 1241017009 26070 80.91.229.2 (29 Apr 2009 14:56:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2009 14:56:49 +0000 (UTC) To: categories Original-X-From: cat-dist Tue Nov 4 13:35:12 1997 Original-Received: by mailserv.mta.ca; id AA30899; Tue, 4 Nov 1997 13:34:16 -0400 Original-Lines: 15 Xref: news.gmane.org gmane.science.mathematics.categories:513 Archived-At: Date: Tue, 4 Nov 1997 16:55:54 +0000 From: Dr. P.T. Johnstone Just a thought about Vaughan's original question: the class of toposes (and that of pretoposes) is stable under slicing, as are all the `exactness properties' that they share with abelian categories. Slices of abelian categories aren't abelian; but, thanks to Aurelio Carboni, we know how to characterize them. So we ought surely to be looking for a common generalization, not of toposes and abelian categories, but of (pre)toposes and affine categories in Aurelio's sense. How about it, Peter? Peter J.