Deformation theory of group schemes and Construction of extensions

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The group scheme over a discrete valuation ring which gives a deformation of a Witt group scheme to a torus is completely determined by giving a filtered structure on it. Among those groups schemes, we can specify which group scheme is stangard as a group scheme which gives the unified Kummer-Artin-Shcreier-Witt theory, and morover in lower degree cases we can show the uniqueness of such a normalized stangard group scheme.The group scheme over a discrete valuation ring which gives a deformation of a Witt group scheme to a torus has a relationship with the unit group scheme of a group-ring scheme. In fact, we can analyze the structure of the unit group schemes of those group-ring schemes, and in a lower dimensional case we can decide the explicit relationship between the stangard deformation group schemes and such unit group schemes.To construct the group schemes over a discrete valuation ring which gives a deformation of a Witt group scheme to a torus, we need to compute the homomorphism groups and cohomology groups of group schemes over an Artin local ring. When the Artin local ring is F_p-algebra, we could compute completely those groups.In the future, the works which should be done are to conpactify the group schemes over a discrete valuation ring which gives a deformation of a Witt group scheme to a torus, and to decide the homomorphism groups and cohomology groups of group schemes over an Artin local ring when it is Z/p^n-algebra. We beleave that the fundamental methods of treating those works have been already given.