Invariance of the Gibbs measure for the Benjamin-Ono equation

Abstract

In this paper we consider the periodic Benjamin-Ono equation. We establish the invariance of the Gibbs measure associated to this equation, thus answering a question raised in Tzvetkov [28]. As an intermediate step, we also obtain a local well-posedness result in Besov-type spaces rougher than L 2, extending the L 2 well-posedness result of Molinet [20].