209 名前: also the infinite versions of these objects as limits of sequences of inclusions of finite objects of ever increasing size.
Moreover, ind-categories allow one to handle “big things in terms of small things” also in another important sense: many large categories are actually (equivalent to) ind-categories of small categories. This means that, while large, they are for all practical purposes controlled by a small category (see the description of the hom-set of Ind(C) in terms of that of C below). Such large categories equivalent to ind-categories are therefore called accessible categories.
8. References Ind-categories were introduced in
http://sage.math.washington.edu/home/wstein/www/home/craigcitro/sga4/Grothendieck/SGA4/sga41.pdf Alexander Grothendieck, Jean-Louis Verdier in SGA4 Exp. 1 pdf file