L2 Cohomology and Warped Products and Arithmetic Groups.
L’azione del gruppo simplettico associata ad un’estensione quadratica di campi
Les nombres de Tamagawa de groupes semi-simples
Local Borcherds products
The local Picard group at a generic point of the one-dimensional Baily-Borel boundary of a Hermitean symmetric quotient of type is computed. The main ingredient is a local version of Borcherds’ automorphic products. The local obstructions for a Heegner divisor to be principal are given by certain theta series with harmonic coefficients. Sometimes they generate Borcherds’ space of global obstructions. In these particular cases we obtain a simple proof of a result due to the first author: Suppose...