Sharp well-posedness results for the Schrödinger-Benjamin-Ono system (Q5962993)

The author studies the coupled Schrödinger-Benjamin-Ono system NEWLINE\[NEWLINE\begin{aligned} i\partial_{t}u+\partial_{x}^{2}u & =\alpha u v, \\ \partial_{t}v+\nu\mathcal{H}\partial_{x}^{2}v & =\beta\partial_{x}(|u|^{2}).\end{aligned} NEWLINE\]NEWLINE Here, \(\mathcal{H}\) is the Hilbert transform, and the independent variable \(x\) is taken to be in \(\mathbb{R}\). The non-resonant case is the case in which \(|\nu|\neq 1\). Prior existence results have been established, showing well-posedness of this system in the Sobolev spaces \(H^{s}\times H^{s-1/2}\).NEWLINENEWLINEHere, the author studies well-posedness in \(H^{s}\times H^{s'}\), without requiring \(s'=s-1/2.\) Under certain conditions on \(s\), \(s'\), local well-posedness is proved. Furthermore, in both the resonant and non-resonant cases, for a variety of values of \(s\), \(s'\), the failure of the solution map to be \(C^{2}\) is proved.