Groupes de Whitehead de groupes algébriques simples sur un corps
Homological Properties of Certain Arithmetic Groups in the Function Field Case.
Integral quadratic forms : applications to algebraic geometry
L’azione del gruppo simplettico associata ad un’estensione quadratica di campi
Modelování ve vědě a technice
Normalteiler ganzzahliger Spingruppen.
Note über das Geschlecht gewisser arithmetischer Gruppen.
On automorphism groups of -adic Schottky curves
On Invariant Measures, Minimal Sets and a Lemma of Margulies.
On the Generation of Dyadic Integral Orthogonal Groups.
On the isomorphisms of the projective orthogonal groups and their congruence subgroups.
On the Maximality of the Orthogonal Groups in the Symplectic Groups in Characteristic Two.
On the orthogonal groups of unimodular quadratic forms. II.
On volumes of arithmetic quotients of
We apply G. Prasad’s volume formula for the arithmetic quotients of semi-simple groups and Bruhat-Tits theory to study the covolumes of arithmetic subgroups of . As a result we prove that for any even dimension there exists a unique compact arithmetic hyperbolic -orbifold of the smallest volume. We give a formula for the Euler-Poincaré characteristic of the orbifolds and present an explicit description of their fundamental groups as the stabilizers of certain lattices in quadratic spaces. We...
Orthogonal representations of Galois groups, Stiefel-Whitney classes and Hasse-Witt invariants.
Principe de hasse faible pour les systèmes de formes quadratiques.
Principe de Hasse pour les espaces principaux homogènes sous les groupes classiques sur un corps de dimension cohomologique virtuelle au plus 1.
Purity of level stratifications
Let be a field of characteristic . Let be a over (i.e., an -truncated Barsotti–Tate group over ). Let be a -scheme and let be a over . Let be the subscheme of which describes the locus where is locally for the fppf topology isomorphic to . If , we show that is pure in , i.e. the immersion is affine. For , we prove purity if satisfies a certain technical property depending only on its -torsion . For , we apply the developed techniques to show that all level ...
Ramification in p-Adic Lie Extensions.
Rational fixed points for linear group actions
We prove a version of the Hilbert Irreducibility Theorem for linear algebraic groups. Given a connected linear algebraic group , an affine variety and a finite map , all defined over a finitely generated field of characteristic zero, Theorem 1.6 provides the natural necessary and sufficient condition under which the set contains a Zariski dense sub-semigroup ; namely, there must exist an unramified covering and a map such that . In the case , is the additive group, we reobtain the...