Good properties of algebras of invariants and defect of linear representations.
Let be a positive integer and a complete characteristic zero discrete valuation ring with maximal ideal , absolute ramification index and perfect residue field of characteristic . In this paper we classify smooth finite dimensional formal -faithful groups over , i.e. groups on which the “multiplication by ” morphism is faithfully flat, in particular -divisible groups. As applications, we prove that -divisible groups over , and the morphisms between them, lift canonically to , and...
Le groupe de Cremona est connexe en toute dimension et, muni de sa topologie, il est simple en dimension .