Ha. Biagioni et F. Linares, Ill-posedness for the derivative Schrodinger and generalized Benjamin-Ono equations, T AM MATH S, 353(9), 2001, pp. 3649-3659
Ill-posedness is established for the initial value problem (IVP) associated
to the derivative nonlinear Schrodinger equation for data in H-s (R), s <
1/2. This result implies that best result concerning local well-posedness f
or the IVP is in H-s ( R), s <greater than or equal to> 1/2. It is also sho
wn that the (IVP) associated to the generalized Benjamin-Ono equation for d
ata below the scaling is in fact ill-posed.