Which weakly ramified group actions admit a universal formal deformation?
نویسنده
چکیده
We determine exactly which formal deformation functors of representations of a finite group as weakly ramified automorphisms of a power series ring over a perfect field of positive characteristic are prorepresentable: only in characteristic two, the weak action of an involution and of the Klein group have non-pro-representable mixedcharacteristic formal deformation functors, and only the first of those has a nonprorepresentable equicharacteristic deformation functor. Examples of such representations are provided by a group action on an ordinary curve: the action of a ramification group on the completed local ring of any point on such a curve is weakly ramified.
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