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Thursday, May 12th, 2011
Time 
Event 
1:13p 
leave a Grothendieck universe искрометный пассаж из википедии: There is another approach to universes which is historically connected with category theory. This is the idea of a Grothendieck universe. Roughly speaking, a Grothendieck universe is a set inside which all the usual operations of set theory can be performed. For example, the union of any two sets in a Grothendieck universe U is still in U. Similarly, intersections, unordered pairs, power sets, and so on are also in U. This is similar to the idea of a superstructure above. The advantage of a Grothendieck universe is that it is actually a set, and never a proper class. The disadvantage is that if one tries hard enough, one can leave a Grothendieck universe.  2:25p 
David Corfield Не забыть почитать Towards a Philosophy of Real Mathematics.  4:04p 

