A home-made Hartshorne-Serre correspondence.
A homological criterion for reducibility of analytic spaces, with application to characterizing the theta divisor of a product of two general principally polarized abelian varieties.
A homological proof of a theorem by Davis, Geramita, Orecchia giving the Cayley-Bacharach theorem.
A Kummer criterion for imaginary quadratic fields
À la recherche de petites sommes d'exponentielles
Soit une fraction rationnelle à coefficients entiers, vérifiant des hypothèses assez générales. On prouve l’existence d’une infinité d’entiers , ayant exactement deux facteurs premiers, tels que la somme d’exponentielles soit en , où est une constante ne dépendant que de la géométrie de . On donne aussi des résultats de répartition du type Sato-Tate, pour certaines sommes de Salié, modulo , avec entier comme ci- dessus.
A Lax formalism for the elliptic difference Painlevé equation.
A Lefschetz decomposition for Chow motives of abelian schemes.
A limit linear series moduli scheme
We develop a new, more functorial construction for the basic theory of limit linear series, which provides a compactification of the Eisenbud-Harris theory. In an appendix, in order to obtain the necessary dimensional lower bounds on our limit linear series scheme we develop a theory of “linked Grassmannians”; these are schemes parametrizing sub-bundles of a sequence of vector bundles, which map into one another under fixed maps of the ambient bundles.
A linear bound on the t-normality of codimension two subvarieties of ...n.
A linear extension operator for Whitney fields on closed o-minimal sets
A continuous linear extension operator, different from Whitney’s, for -Whitney fields (p finite) on a closed o-minimal subset of is constructed. The construction is based on special geometrical properties of o-minimal sets earlier studied by K. Kurdyka with the author.
A local Bernstein inequality on real algebraic varieties.
A local-global principle for rational isogenies of prime degree
Let be a number field. We consider a local-global principle for elliptic curves that admit (or do not admit) a rational isogeny of prime degree . For suitable (including ), we prove that this principle holds for all , and for , but find a counterexample when for an elliptic curve with -invariant . For we show that, up to isomorphism, this is the only counterexample.
A look into the Severi varieties of curves in higher codimension.
A Mackey Imprimitivity Theory for Algebraic Groups.
A mathematical proof of a formula of Aspinwall and Morrison
A Measure for Semialgebraic Sets Related to Boolean Complexity.
A memoir on the double ...-functions.
A metric graph satisfying [...] w 4 1 = 1 that cannot be lifted to a curve satisfying [...] dim ( W 4 1 ) = 1
For all integers g ≥ 6 we prove the existence of a metric graph G with [...] w41=1 such that G has Clifford index 2 and there is no tropical modification G′ of G such that there exists a finite harmonic morphism of degree 2 from G′ to a metric graph of genus 1. Those examples show that not all dimension theorems on the space classifying special linear systems for curves have immediate translation to the theory of divisors on metric graphs.
A minimal Set of Generators for the Ring of multisymmetric Functions
The purpose of this article is to give, for any (commutative) ring , an explicit minimal set of generators for the ring of multisymmetric functions as an -algebra. In characteristic zero, i.e. when is a -algebra, a minimal set of generators has been known since the 19th century. A rather small generating set in the general case has also recently been given by Vaccarino but it is not minimal in general. We also give a sharp degree bound on the generators, improving the degree bound previously...
A modular compactification of the general linear group.