On formal groups obtained from symmetric powers
On formal groups over complete discrete valuation rings with application to a theorem of Lutz.
On functional equations of complex powers.
On Hironaka's Additive Groups Associated with Points in Projective Space.
On hypersurface quotient singularities of dimension 4.
On induced actions of algebraic groups
In this paper we study the existence problem for products in the categories of quasi-projective and algebraic varieties and also in the category of algebraic spaces.
On inseparable descent
On invariants of a set of matrices.
On J1 (p) and the kernel of the Eisenstein ideal.
On metacyclic extensions
Galois extensions with various metacyclic Galois groups are constructed by means of a Kummer theory arising from an isogeny of certain algebraic tori. In particular, our method enables us to construct algebraic tori parameterizing metacyclic extensions.
On non-basic Rapoport-Zink spaces
In this paper we study certain moduli spaces of Barsotti-Tate groups constructed by Rapoport and Zink as local analogues of Shimura varieties. More precisely, given an isogeny class of Barsotti-Tate groups with unramified additional structures, we investigate how the associated (non-basic) moduli spaces compare to the (basic) moduli spaces associated with its isoclinic constituents. This aspect of the geometry of the Rapoport-Zink spaces is closely related to Kottwitz’s prediction that their -adic...
On norm maps for one dimensional formal groups. II. ...-extensions of local fields with algebraically closed residue field.
On normal representations of G-actions on projective varieties.
On observable subgroups of complex analytic groups and algebraic structures on analytic homogeneous spaces.
On orbits of the automorphism group on an affine toric variety
Let X be an affine toric variety. The total coordinates on X provide a canonical presentation of X as a quotient of a vector space by a linear action of a quasitorus. We prove that the orbits of the connected component of the automorphism group Aut(X) on X coincide with the Luna strata defined by the canonical quotient presentation.
On quasihomogeneous manifolds – via Brion-Luna-Vust theorem
We consider a smooth projective variety on which a simple algebraic group acts with an open orbit. We discuss a theorem of Brion-Luna-Vust in order to relate the action of with the induced action of on the normal bundle of a closed orbit of the action. We get effective results in case and .
On reduction of Hilbert-Blumenthal varieties
Let be the ring of integers of a totally real field of degree . We study the reduction of the moduli space of separably polarized abelian -varieties of dimension modulo for a fixed prime . The invariants and related conditions for the objects in the moduli space are discussed. We construct a scheme-theoretic stratification by -types on the Rapoport locus and study the relation with the slope stratification. In particular, we recover the main results of Goren and Oort [J. Alg. Geom.,...
On representations of with algebras of invariants being complete intersections.
On sections of commutative group schemes
On semi-invariants of tilted algebras of type Aₙ
We prove that for algebras obtained by tilts from the path algebras of equioriented Dynkin diagrams of type Aₙ, the rings of semi-invariants are polynomial.