Infinitesimally Central Extensions of Chevalley Groups

Conventions.- Universal central extensions. Central trick.- Degenerate sums. The extension r : .- The action . Structure of g*Z, g*R.- Admissible lattices and the category LV. ?-connected components.- The G-module ker ?.- G-invariant [p]-structures.- The extension ? : G* ? G.- Extensions of G by a G-module.- The hochschild groups.- The existence of ? : G* ? G.- Relations in the open cell.- Representatives in G* of the Weyl group.- The theorem of generators and relations and its consequences.- The group functor G*.