Summary: This is a summary of the author’s results on finite flat commutative group schemes. The properties of the generic fibre functor are discussed. A complete classification of finite local flat commutative group schemes over mixed characteristic complete discrete valuation rings in terms of their Cartier modules (defined by Oort) is given. We also state several properties of the tangent space of these schemes. These results are applied to the study of reduction of abelian varieties. A finite \(p\)-adic semistable reduction criterion is formulated. It looks especially nice in the ordinary reduction case. The plans of the proofs are described.
For the entire collection see [Zbl 1083.11004].