El principal objetivo es analizar la extensión de un G-torsor dado sobre la fibra genérica de X, donde X=AnRes el espacio afín n-dimensional sobre un anillo de valuación discreta R. Para ello primero se estudiará ...

Given a relative faithfully at pointed scheme over the spectrum of a discrete valuation ring X !S, this paper is motivated by the study of the natural morphism from the fundamental group scheme of the generic ber X ...

Let X := A n R be the n-dimensional affine space over a discrete valuation ring R with fraction field K. We prove that any pointed torsor Y over A n K under the action of an affine finite-type group scheme can be extended ...

Corrección de datos publicados en “Heights of vector bundles and the fundamental group scheme of a curve”

Let R be a discrete valuation ring with fraction field K. Let X be a proper and faithfully flat R-scheme, endowed with a section x∈X(R), with connected and reduced generic fibre Xη. Let f:Y→Xη be a finite Nori-reduced ...

We prove the existence of a Galois closure for towers of torsors under finite group schemes over a proper, geometrically connected and geometrically reduced algebraic stack X over a field k. This is done by describing the ...

Soient S un schéma de Dedekind, X un S-schéma connexe localement de type ni et x 2 X(S) une section. L’objet du présent papier est d’établir l’existence du schéma en groupes fondamental de X lorsque X est à bres réduites ...

Let X be any scheme defined over a Dedekind scheme S with a given section x ∈ X (S). We prove the existence of a pro-finite S-group scheme א (X,x) and a universal א (X,x)-torsor dominating all the pro-finite pointed torsors ...

Si X es un esquema propio, suave y conexo sobre Spec(R), para R un anillo de valuación discreta completo, dotado de una sección x: Spec(R) -> X, es posible construir los esquemas fundamentales en grupos pi_1(X,x) y ...