see also Drinfeld's paper onthe arXiv @2002 on DG categories Jim Stasheff jds@math.upenn.edu Home page: www.math.unc.edu/Faculty/jds As of July 1, 2002, I am Professor Emeritus at UNC and I will be visiting U Penn but for hard copy the relevant address is: 146 Woodland Dr Lansdale PA 19446 (215)822-6707 On Wed, 11 Jan 2006, Andree Ehresmann wrote:
In answer to the question raised by Jean:
if C is a category, what does one need to assume on a subcategory V of C to be able to construct an analogous C/V and what structure does it inherit ?
Charles Ehresmann had studied the problem of the existence of a quotient = (or at least 'quasi-quotient') category of a category by a sub-category, which h= ad led to the introduction of the notion of a "proper subcategory" (generalizing distinguished sub-groups). His results, summarized in a Note (CRAS Paris= 260, 2116) are developed in the paper on non-abelian cohomology "Cohomologie a valeurs dans une categorie dominee" (Collloque Topologie Bruxelles, CBRM = 1866) . Both papers are reprinted in "Charles Ehresmann: Oeuvres completes et commentees" Part III-2 (and partially taken back in his book "Categories = et structures", Dunod 1965). With all my best wishes Andree Ehresmann.