Grothendieck introduced crystalline cohomology to study the p-torsion part of the cohomology of characteristic p varieties. In the crystalline topology, which is the basis of this theory, the underlying category has objects given by infinitesimal thickenings together with divided power structures. Crystalline sites are examples of sites with no final object.
Grothendieck introduced crystalline cohomology to study the p-torsion part of the cohomology of characte.ristic p varieties In the crystalline topology which is the basis of this theory the underlying category has objects given by infinit,esimal thickenings together with divided power structures. Crystalline sites are examples of sites with no final object.