# Sur le changement de signe des sommes de Kloosterman

### Abstract

Combining sieve methods with automorphic form theory and techniques from $\ell$-adic cohomology, we prove that the sign of Kloosterman sums ${\mathrm{Kl}}(1,1;n)$ changes infinitely often as $n$ ranges over the squarefree integers having all their prime factors larger than $n^{1/23.9}$.

## Authors

Étienne Fouvry

Mathématiques Bât
Univ. Paris-Sud, Campus d'Orsay
F-91405 Orsay Cedex
France

Philippe Michel

Département de Mathématiques
Univ. Montpelier II
Place E. Bataillon
FR-34095 Montpellier Cedex
France