4 Jul
2011
4 Jul
'11
11:11 p.m.
Concerning Eduardo's question: Now, if you work with a Grothendieck base topos “as if it were the category of sets”, you are forced to specify which small category of finite sets you are using, or not ?. No, in the definition of an U-topos, E, given in SGA 4, Expose IV, § 1, it is required that E has an U-small (topologically) generating set of objects. Bu such a set or, equivalently, full subcategory of E, is not part of the data. Bill Messing [For admin and other information see: http://www.mta.ca/~cat-dist/ ]