Subject: Re: 2 responses
Date: Thu, 14 Mar 2002 11:03:10 -0500 (Eastern Standard Time)
From: "Nicholas J. Kuhn"
To: Don Davis
CC: njk4x@virginia.edu
A little comment about categories where morphisms are diagrams
G_1 --> H <-- G_2 ...
This `category' is NOT a category in general, because the morphisms
from G_1 to G_2 will not be a set (and one bumps up against Russell's
paradox). This, of course, is a well known and fundamental problem to
all who work with localizations and model categories.
The simplest fix is to restrict the construction to a small category
(i.e. a set's worth of objects).
Nick Kuhn