Weak normality and Lipschitz saturation for ordinary singularities
A singularity is said to be weakly-exceptional if it has a unique purely log terminal blow-up. In dimension 2, V. Shokurov proved that weakly-exceptional quotient singularities are exactly those of types D n, E 6, E 7, E 8. This paper classifies the weakly-exceptional quotient singularities in dimensions 3 and 4.
Consider a representation of a finite group as automorphisms of a power series ring over a perfect field of positive characteristic. Let be the associated formal mixed-characteristic deformation functor. Assume that the action of is weakly ramified, i.e., the second ramification group is trivial. Example: for a group action on an ordinary curve, the action of a ramification group on the completed local ring of any point is weakly ramified.We prove that the only such that are not pro-representable...