In this paper, we prove the asymptotic stability of the family of
solitons of the Benjamin-Ono equation in the energy space. The
proof is based on a Liouville property for solutions close to the
solitons for this equation, in the spirit of [Martel, Y. and Merle, F.:
Asymptotic stability of solitons for subcritical generalized KdV
equations. Arch. Ration. Mech. Anal. 157 (2001), 219-254],
[Martel, Y. and Merle, F.: Asymptotic stability of solitons of the gKdV
equations with a general nonlinearity. Math. Ann. 341 (2008), 391-427].
As a corollary of the proofs, we obtain the asymptotic stability of
exact multi-solitons.