10 citations · 30 across the 16 of their papers we have counts for
20 papers
Decidability of singularities in the Ekedahl--Oort stratification
Jean-Stefan Koskivirta, Lorenzo La Porta
For an abelian type Shimura variety and an odd prime of good reduction, we characterize the regularity in codimension one of Zariski closures of Ekedahl--Oort strata in terms o…
Singularities in the Ekedahl--Oort stratification
Jean-Stefan Koskivirta, Lorenzo La Porta, Stefan Reppen
We give conceptual and combinatorial criteria for the normality and Cohen--Macaulayness of unions of Ekedahl--Oort strata in the special fiber of abelian type Shimura varieties. Fo…
The cone conjecture for vector-valued Siegel automorphic forms
Jean-Stefan Koskivirta
We prove that the effective cone of automorphic vector bundles on the Siegel modular variety of rank in characteristic at a place of good reduction is encoded by the stack…
The stack of -zips is a Mori dream space
Jean-Stefan Koskivirta
We first extend previous results of the author with T. Wedhorn and W. Goldring regarding the existence of -ordinary Hasse invariants for Hodge-type Shimura varieties to other au…
Cohomology vanishing for Ekedahl--Oort strata on Hilbert--Blumenthal Shimura varieties
Jean-Stefan Koskivirta
We prove vanishing results for the th cohomology of automorphic line bundles on the Ekedahl--Oort strata of the special fiber of Hilbert--Blumenthal Shimura varieties. This work…
A vanishing theorem for vector-valued Siegel automorphic forms in characteristic
Jean-Stefan Koskivirta
We show that the space of vector-valued Siegel automorphic forms in characteristic is zero when the weight is outside of an explicit locus. This result is a special case of a g…
Griffiths-Schmid conditions for automorphic forms via characteristic
Wushi Goldring, Jean-Stefan Koskivirta
We establish vanishing results for spaces of automorphic forms in characteristic and characteristic . We prove that for Hodge-type Shimura varieties, the weight of any nonze…
Divisibility of mod automorphic forms and the cone conjecture for certain Shimura varieties of Hodge-type
Wushi Goldring, Jean-Stefan Koskivirta
For several Hodge-type Shimura varieties of good reduction in characteristic , we show that the cone of weights of automorphic forms is encoded by the stack of -zips of Pink-…
Weights of mod automorphic forms and partial Hasse invariants
Wushi Goldring, Naoki Imai, Jean-Stefan Koskivirta
For a connected, reductive group over a finite field endowed with a cocharacter , we define the zip cone of as the cone of all possible weights of mod automorphi…
Partial Hasse invariants for Shimura varieties of Hodge-type
Naoki Imai, Jean-Stefan Koskivirta
For a connected reductive group over a finite field, we define partial Hasse invariants on the stack of -zip flags. We obtain similar sections on the flag space of Shimura v…
Automorphic vector bundles on the stack of -zips
Naoki Imai, Jean-Stefan Koskivirta
For a connected reductive group over a finite field, we study automorphic vector bundles on the stack of -zips. In particular, we give a formula in the general case for the…
Automorphic forms on the stack of G-Zips
Jean-Stefan Koskivirta
Improved version. To appear in Results in Mathematics.
Quasi-constant characters: Motivation, classification and applications
Wushi Goldring, Jean-Stefan Koskivirta
In our previous paper "Strata Hasse invariants, Hecke algebras and Galois representations", initially motivated by questions about the Hodge line bundle of a Hodge-type Shimura var…
Normalization of closed Ekedahl-Oort strata
Jean-Stefan Koskivirta
We apply our theory of partial flag spaces developed in previous articles to study a group-theoretical generalization of the canonical filtration of a truncated Barsotti-Tate group…
Automorphic vector bundles with global sections on --schemes
Wushi Goldring, Jean-Stefan Koskivirta
A general conjecture is stated on the cone of automorphic vector bundles admitting nonzero global sections on schemes endowed with a smooth, surjective morphism to a stack of -z…
Stratifications of flag spaces and functoriality
Wushi Goldring, Jean-Stefan Koskivirta
We define quotient stacks of "zip flags". They form towers above the stack of -zips introduced by Moonen, Pink, Wedhorn and Ziegler. We define a stratification on the stack of z…
Strata Hasse invariants, Hecke algebras and Galois representations
Wushi Goldring, Jean-Stefan Koskivirta
We construct group-theoretical generalizations of the Hasse invariant on strata closures of the stacks -Zip. Restricting to zip data of Hodge type, we obtain a group-theoret…
Sections of the Hodge bundle over Ekedahl-Oort strata of Shimura varieties of Hodge type
Jean-Stefan Koskivirta
We construct canonical non-vanishing global sections of powers of the Hodge bundle on each Ekedahl-Oort stratum of a Hodge type Shimura variety. In particular we recover the quasi-…
Generalized mu-ordinary Hasse invariants
Jean-Stefan Koskivirta, Torsten Wedhorn
We construct canonical Hasse invariants for arbitrary Shimura varieties of Hodge type for the mu-ordinary locus.
Congruence relations for Shimura varieties associated to unitary groups
Jean-Stefan Koskivirta
We prove the congruence relation for the mod-p reduction of Shimura varieties associated to a unitary similitude group GU(n-1,1), when p is inert and n odd. When n is even, this re…