Sur la semi-norme spectrale supérieure des algèbres de Banach ultramétrique.
Using rather elementary and direct methods, we first recover and add on some results of Aikawa-Hirata-Lundh about the Martin boundary of a John domain. In particular we answer a question raised by these authors. Some applications are given and the case of more general second order elliptic operators is also investigated. In the last parts of the paper two potential theoretic results are shown in the framework of uniform domains or the framework of hyperbolic manifolds.
On se propose d’établir le Théor`eme de Bartle-Graves dans la catégorie des quotients bornologiques. Aussi, cela nous permet de définir certains espaces de fonctions `a valeurs dans des quotients bornologiques.