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A geometric application of Nori’s connectivity theorem

Claire Voisin (2004)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

We study (rational) sweeping out of general hypersurfaces by varieties having small moduli spaces. As a consequence, we show that general K -trivial hypersurfaces are not rationally swept out by abelian varieties of dimension at least two. As a corollary, we show that Clemens’ conjecture on the finiteness of rational curves of given degree in a general quintic threefold, and Lang’s conjecture saying that such varieties should be rationally swept-out by abelian varieties, contradict.

À la recherche de petites sommes d'exponentielles

Étienne Fouvry, Philippe Michel (2002)

Annales de l’institut Fourier

Soit f ( x ) une fraction rationnelle à coefficients entiers, vérifiant des hypothèses assez générales. On prouve l’existence d’une infinité d’entiers n , ayant exactement deux facteurs premiers, tels que la somme d’exponentielles x = 1 n exp ( 2 π i f ( x ) / n ) soit en O ( n 1 2 - β f ) , où β f > 0 est une constante ne dépendant que de la géométrie de f . On donne aussi des résultats de répartition du type Sato-Tate, pour certaines sommes de Salié, modulo n , avec n entier comme ci- dessus.

A proof of the stratified Morse inequalities for singular complex algebraic curves using the Witten deformation

Ursula Ludwig (2011)

Annales de l’institut Fourier

The Witten deformation is an analytic method proposed by Witten which, given a Morse function f : M R on a smooth compact manifold M , allows to prove the Morse inequalities. The aim of this article is to generalise the Witten deformation to stratified Morse functions (in the sense of stratified Morse theory as developed by Goresky and MacPherson) on a singular complex algebraic curve. In a previous article the author developed the Witten deformation for the model of an algebraic curve with cone-like singularities...

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