Every category admits a Grothendieck topology, called canonical, which is the finest topology which makes representable functor into sheaves.


Is there a concrete description of the canonical topology on the category of schemes? By Grothendieck's results on descent this is at least as fine as the fpqc topology, but I don't even know if the two actually coincide. If not, what is known about it?



Canonical topology on the category of schemes?
Proposition 3.4 in Orlov's paper 


Quasicoherent sheaves in commutative and noncommutative geometry. (Russian) Izv. Ross. Akad. Nauk Ser. Mat. 67 (2003), no. 3, 119--138; translation in Izv. Math. 67 (2003), no. 3, 535--554.


describes the canonical topology and the universally strict epimorphisms on the category of affine schemes. In the same paper Orlov characterizes the quasicoherent sheaves on the small Zariski site in terms of the canonical topology. He also studies an important subcanonical topology - the effective descent topology - which seems to be finer than the flat topology. 


